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Ionospheric Telecommunication

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Ionosphere and radiowave propagation

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									                                 COST 251TD(97)010
                                 October 1997




    Second Annual Report
(period July 1996 - June 1997)

                                 R Hanbaba
                                 Chairman
                                 October 1997
                                                                          Table of contents

1. Objectives ................................................................................................................................................................2
2. Participating Countries and Institutes.......................................................................................................................2
3. Project structure.......................................................................................................................................................4
4. Management Committee and related meetings .........................................................................................................5
   4.1 Management Committee meetings, Working Group Sessions and Workshops ...................................................5
     4.1.1: Fourth Management Committee meeting and first Workshop of COST 251................................................5
     4.1.2: Fifth Management Committee meeting and Joint COST 251/IRI Workshop ...............................................5
   4.2 Other meetings...................................................................................................................................................6
5. Method of working and project timescales................................................................................................................7
6. Progress to date......................................................................................................................................................10
   6.1 Working Group 1 Models for terrestrial systems...............................................................................................10
     6.1.1: Data Bank ................................................................................................................................................10
     6.1.2: Oblique sounding and short-term vertical measurements ..........................................................................12
     6.1.3: Single Station Models (SSM) ...................................................................................................................12
     6.1.4: Profile and Models ...................................................................................................................................12
     6.1.5: Target ranging and location......................................................................................................................12
   6.2 Working Group 2 Models for Earth-space systems ...........................................................................................14
   6.3 Working Group 3 Ionospheric modelling .........................................................................................................20
     6.3.1: Monthly median mapping.........................................................................................................................20
        6.3.1.1 New indices of ionospheric state .........................................................................................................20
        6.3.1.2 Long-term trends of ionospheric change .............................................................................................20
        6.3.1.3 Monthly-median mapping techniques .................................................................................................20
        6.3.1.4 New procedure....................................................................................................................................21
        6.3.1.5 Testing development...........................................................................................................................22
     6.3.2: Instantaneous mapping.............................................................................................................................22
        6.3.2.1 Instantaneous mapping applications....................................................................................................22
        6.3.2.2 Screen-point locations and values specifications..................................................................................23
     6.3.3: Electron density height profile..................................................................................................................24
        6.3.3.1 Development of model ........................................................................................................................24
        6.3.3.2 Establishment of a data set for testing .................................................................................................24
   6.4 Working Group 4 System performance and spectrum management ..................................................................24
   6.5 Working Group 5 Variability and forecasting...................................................................................................25
     6.5.1: High latitude ionospheric variability.........................................................................................................25
     6.5.2: Variability statistics..................................................................................................................................25
     6.5.3: Disturbances.............................................................................................................................................25
     6.5.4: Short-term forecast model ........................................................................................................................27
     6.5.5: Ionospheric Despatch Centre for Europe...................................................................................................28
7. Acknowledgements................................................................................................................................................29
8. References and bibliography ..................................................................................................................................29
9. Other presentations at meetings .............................................................................................................................34
Annex I .....................................................................................................................................................................36
Annex II ....................................................................................................................................................................38




                                                                                      1
1.       Objectives

The main objectives of the Action, embodied in the agreed Memorandum of Understanding, are:

• to demonstrate the practical improvement to terrestrial and Earth-space radio systems of COST 238 derived
  ionospheric models and to promote their use,

• to further refine these models and to widen their geographical area of applicability between latitudes of 35-70°N
  and longitudes of 10°  W-60° E,

• to collect additional quantities and types of ionospheric information and to extend the models to give system
  performance statistics.




2.       Participating Countries and Institutes

The member states are Austria, Belgium, Czech Republic, Germany, Greece, Italy, Poland, Slovenia, Spain, Sweden,
Turkey, United Kingdom. In the process of signing are France and Hungary. Considering participation are Portugal
and Finland.

Participation in Action from non-COST countries are:

Bulgarian Academy of Sciences, Geophysical Institute
Academy of Sciences, Izmiran, Russia
Institute of Radiophysics, St Petersburg, Russia
Institute for Applied Geophysics, Russia

In process of applying for participation:

Geomagnetic Institute, Grocka, Serbia
Ionospheric prediction Service, Australia
Institute of Ionosphere, Almaty, Kazakstan




                                                          2
The following Table gives a list of participating institutes and numbers of personnel involved


Table 1        Participating institutes and number of personnel involved (1996-97)

COUNTRY                        ORGANISATION                                                      PERSONNEL

Austria                        University of Graz                                                    5
Belgium                        Royal Meteorological Institute                                        1
                               KU Leuven, ESAT-TELEMIC                                               1
Bulgaria                       Geophysical Institute                                                 4
Czech Republic                 Institute of Atmospheric Physics                                      5
Germany                        University of Rostock                                                 2
                               DLR, Station Neustrelitz                                              1
Finland                        Geophysical Observatory, Sondankyla                                   1
France                         France Telecom CNET                                                   4
                               Université de Paris Sud, LETTI                                                1
                               Université de Rennes 1, Laboratoire Radiocommunications               1
Greece                         University of Thessaloniki                                            3
Italy                          Istituto Nazionale di Geofisica                                       7
                               International Centre for Theoretical Physics, Trieste                 2
                               National Research Council, IROE, Florence                             2
Kazakstan                      Institute of Ionosphere, Academy of Sciences, Almaty                  1
Poland                         Space Research Centre                                                 3
Russia                         Institute Terrestrial Magnetism, Ionosphere & Radiowave Propagation   7
                               Institute of Radiophysics, St. Petersburg                             3
                               Institute for Applied Geophysics                                      1
Serbia                         Geomagnetic Institute                                                 1
Spain                          Observatori de l'Ebre                                                 3
                                                                                       El
                               Instituto Nacional de Tecnica Aerospacial, Estacion de ‘ Arenosillo’  3
                               Escuela Tecnica Superior de Ingenieros de Telecomunicaciones, Madrid 1
                                                                  La
                               Escuela de Telecomunicaciones ‘ Salle’                                1
                               Universidad Complutense Madrid - Facultad Fisicas                     2
Sweden                         Defence Research Establishment                                        3
                               Institute of Space Physics                                            1
                               Ministry for Foreign Affairs                                          1
Turkey                         Middle East Technical University                                      3
                               MRC TUBITAK                                                           1
                               Hacettepe University                                                  2
                               Baskent University                                                    1
                               Barkod Bilgisayarli Kontrol Sistemleri                                1
United Kingdom                 Rutherford Appleton Laboratory                                        5
                               Leeds University                                                      3
                               Lancaster University                                                  1
                               University College of Wales                                           3
                               DRA, Space and Communications                                         3
                               UMIST                                                                 1
                               Neptune Radar                                                         1
                               JPS Associates                                                        1
Total     17                   42                                                                   97

In addition there is participation by two private experts from Germany and UK, respectively.

A full list of participants appears at Annex I.




                                                           3
3.      Project structure

Chairman                 R Hanbaba, France Telecom CNET, France
Vice-Chairman            B Zolesi, Istituto Nazionale di Geofisica, Italy
Secretary                A Vernon, Rutherford Appleton Laboratory, UK


Working Groups


WG 1 - Models for terrestrial systems
        WG Leader: S Kouris, Aristotelian University of Thessaloniki, Greece + 42 current members
              • interaction with radio users and comparison of their performance data with model results,
                including if possible assessment of value of real-time channel evaluation techniques
              • collection of additional vertical and oblique-path ionospheric data for use with
                instantaneous maps


WG 2 - Models for Earth-space systems
        WG Leader: R Leitinger, University of Graz, Austria + 14 current members
              • investigation of ionospheric propagation effects on radio systems used for navigation,
                geodesy and radio-astronomy


WG 3 - Ionospheric modelling
        WG Leader: Lj R Cander, Rutherford Appleton Laboratory, UK + 47 current members
              • monthly median and instantaneous mapping techniques
              • electron-density height profile modelling
              • computer program development


WG 4 - System Performance and Spectrum Management
        WG Leader: L Barclay, Lancaster University, UK
        WG Vice-Leader: B Lundborg, Defence Research Establishment, Sweden
        + 13 current members
                • signal variability and correlation
                • background noise and interference
                • channel models and simulators
                  HF
                • performance prediction


WG 5 - Variability and Forecasting
       WG Co-Leaders: S M Radicella, ICTP, Trieste, Italy
                           G De Franceschi, Istituto Nazionale di Geofisica, Italy
       + 29 current members
                 •improve prediction of ionospheric variability parameters of interest to HF system planning and
                   operation and other ionospheric telecommunications systems particularly in high latitude
                 • investigate and improve ionospheric forecast for HF system operation




                                                         4
4.       Management Committee and related meetings

4.1      Management Committee meetings, Working Group Sessions and Workshops

                                 s
Two Management Committee meeting’ Working Group Sessions and Workshops have taken place in the past year:


4.1.1: Fourth Management Committee meeting and first Workshop of COST 251

24-28 September 1996 - Institute of Atmospheric Physics, Academy of Sciences, Prague, Czech Republic
(COST251TD(96)034 and COST251TD(96)017).

During the meeting conducted at Prague, the Management Committee adopted a new Action organisation structure.
The work programme has been refined and future plans were formulated. The first Workshop with some 50
participants was associated with the meetings of the five Working Groups and the Management Committee meeting.
In total 11 invited review papers were presented, covering topics in the field of long-term ionospheric mapping and
modelling, instantaneous ionospheric mapping, ionospheric variability, short-term ionospheric forecasting,
measurements, HF channel simulators and system performance:
• development of more accurate single station models
• advances in regional ionospheric mapping
• problems of validation of ionospheric models and new technique of profile derivation
• future of the total electron content data collection and their use for mapping, modelling and nowcasting, role of use
    of regional networks of GPS receivers and ionospheric tomography
• ionospheric weather forecast and ionospheric variability with reference to high latitudes
• current state of instantaneous ionospheric mapping
• classification of electron-density height profile models considering their limitation and needed improvements
• short-term ionospheric forecasting based on IRI model updated by measurements of digital ionosondes
• past, present and future of HF channel simulators
• results of measurements in northern Scandinavia using HF channel simulator DAMSON
• current and developing techniques for operating and planning HF systems


4.1.2: Fifth Management Committee meeting and Joint COST 251/IRI Workshop

26-31 May 1997 - Institute of Atmospheric Physics, Kühlungsborn, Germany (COST251TD(97)007).

The second Workshop was jointly organised by the COSPAR/URSI Working Group ‘              International Reference
Ionosphere’ (IRI) and the COST Action 251. The Workshop was associated with the fifth Management Committee
and Working Groups meetings. From the outset, close liaison has been maintained between the COST Action and
IRI. For example, studies are taking place in a joint COST 251/IRI task group (Leader: Sandro Radicella) on model
descriptions for the bottomside F-region including the F1 layer.

The main aim of this Workshop was to review recent advances in ionospheric modelling and prediction, with
particular emphasis on development of new improved prediction capabilities and was attended by ninety participants
from twenty-two countries, indicating the broadened interest of ionospheric modelling and prediction. A total of eighty
papers were presented (16 invited, 35 contributed and 29 poster papers) in eight sessions with the majors topics as
follows:

•    Bottomside ionosphere (chaired by B Reinisch, United States of America, 6 oral papers and 5 posters),
•    Ionospheric models and HF propagation (chaired by B Lundborg, Sweden, 6 oral papers and 1 poster),
•    E and D region (chaired by D Bilitza, United States of America, 5 oral papers and 3 posters),
•    Topside ionosphere (chaired by R Leitinger, Austria, 7 oral papers and 3 posters),
•    Ionospheric storms and trough (chaired by K Rawer, Germany, 12 oral papers and 2 posters),
•    Long-term variation and variability (chaired by S Radicella, Italy, 7 oral papers and 14 posters),
•    Ion composition and plasma temperatures (chaired by D Anderson, United States of America, 4 oral papers and 1
     poster),

                                                          5
• Ion drift, spread-F and scintillation (chaired by J Grebowsky, United States of America, 4 oral papers).

A high standard of papers covered all directions of the IRI and the largest part of COST 251 activities, including
future trends of ionospheric modelling and prediction. Many new interesting results were presented. Practical ways of
determining monthly median models were shown and short-term changes in the ionosphere were described. In
addition to the widespread disturbances associated with major geophysical or solar events, the hour-to-hour and day-
to-day variations have been analysed. Investigations were introduced towards the development of an ionospheric
forecasting capability, especially under storm conditions. The ionospheric informations needed to improve the
performance of radio systems affected by the ionosphere were considered. There were also presentations and
discussions on observational techniques, including facilities available at the different organisations, and development
of computer programs in accordance with the various procedures. The validity and efficiency of the results of the
regional modelling effort has been now demonstrated and numerous studies show promising results that can be
interfaced with a global model. Finally, comparisons between models and data were made.

The first special session was dedicated to the Memory of Lucien Bossy (past Chairman of IRI) with a Memorial paper
presented by Karl Rawer. A final plenary session was held on the last day of the Workshop to summarise the
highlights of the sessions and to discuss on future problems and directions. In addition, there was one well-attended
poster presentation. Papers presented by the COST 251 participants appear in COST251(TD)007 Part I (Editor A
Vernon) and Part II (Editor B Lundborg). Selected papers are scheduled to appear in Advances in Space Research
(ASR).

Despite the considerable progress reported during the Workshop, the participants are of the opinion that there remains
a lot of further work to be accomplished. This is true for example in the areas of modelling of sporadic-E, spread-F,
scintillation and the vertical distribution of electron density. In particular, efforts should be pursued towards the
development of total electron content (which parameter controls most ionospheric effects on earth-space links) and
day-to-day variability modelling and prediction capabilities.

It was also emphasised during this joint Workshop that this international co-operative research is absolutely necessary.
It is quite understood that COST 251 objectives are more radio engineering applications oriented and IRI gives more
emphasis on radio science, many participants are involved in both areas and find mutual benefit with the
arrangements of the meetings at the same location.


4.2 Other meetings

4.2.1: Meeting on the COST 251 Data bank, ICTP, Trieste, Italy, 20-23 November 1996

The implementation options for the COST 251 data were defined.

4.2.2: Meeting on the use of neural network techniques for forecasting, ICTP, Trieste,
       Italy, 20-25 January 1997
The possible use of Neural Network techniques in the framework of the objectives of COST was examined.

4.2.3: COST 251 HF Channel Simulator Workshop, Leeds, UK, 21-23 January 1997

The meeting was held to formulate a specification for design and architecture of a new high performance ionospheric
simulator. The meeting went on to identify a set of parameters which will need to be specified for the setting up and
operation of the simulator. The appropriate values for these parameters are obtained from the knowledge of the
ionosphere to consider the architecture for a high data rate simulator.

4.2.4: Study visit to the University of Paris Sud, France, 26-31 January 1997

A meeting was held in Paris which discussed the correlation and variability of signals with the objective of further
analysis for inclusion in the modelling of the characteristics of the communication channel.

4.2.5: Meeting on single stations models, Observatori de l'Ebro, Spain, 3-12 April 1997
Test of single stations models for the COST 251 area were achieved.


                                                           6
5.       Method of working and project timescales

                                                       s)                         s
The work is organised as a series of Work Packages (WP’ structured within five WG’ as follows:

Working Group 1 - Models for terrestrial systems

WP 1.1          Data bank:
WP 1.1.1        Data [VI, OI, TEC, etc.]
WP 1.1.2        Quality control
WP 1.1.3        Oblique sounding and short-term vertical measurements

WP 1.2          Maps and models
WP 1.2.1        Single station models
WP 1.2.3        Models for users

WP 1.3          Target ranging and location
                System performance by simulation

Working Group 2 - Models for Earth-space systems

WP 2.1          Status of work
WP 2.2          Extension of the mapping area for monthly median mapping
WP 2.3          TEC variability
WP 2.4          Short term forecasting and now casting of TEC
WP 2.5          Link to the electron density height profile

Working Group 3 - Ionospheric modelling

WP 3.1:         Monthly median mapping techniques
WP 3.1.1        Merit of new ionospheric indices
WP 3.1.2        Long-term trends of ionospheric change
WP 3.1.3        Refinement of PRIME mapping techniques
WP 3.1.4        New monthly median mapping procedures

WP 3.2:         Instantaneous mapping
WP 3.2.1        Instantaneous mapping applications
WP 3.2.2        Screen-point locations and values specifications
WP 3.2.3        Buffer zone
WP 3.2.4        Testing development

WP 3.3          Electron density height profile
WP 3.3.1        Development of model
WP 3.3.2        Adoption of a model
WP 3.3.3        Establishment of a data set for testing

WP 3.4          Computer program and WWW publicity
WP 3.4.1        Computer program
WP 3.4.2        WWW publicity

Working Group 4 - System performance and spectrum management

WP 4.1          Signal variability and correlation
WP 4.1.1        Channel characterisation measurement and modelling
WP 4.1.3        Theoretical aspects - em wave propagation scattering function, general ray-tracing modelling
WP 4.1.4        Signal correlation, coherence constraints




                                                          7
WP 4.2         Background noise and interference
WP 4.2.1       Spectrum occupancy
WP 4.2.2       Atmospheric and man-made noise

WP 4.3         HF channel models and simulators
WP 4.3.1       Review of available simulator techniques
WP 4.3.2       Identification of ionospheric parameters need for simulation
WP 4.3.3       Development of a replacement for the Watterson model

WP 4.4         Performance prediction and real-time frequency management
WP 4.4.1       Definition of requirements for performance prediction models
WP 4.4.2                                                                                  s       s
               Development of prediction modelling techniques using results from other WG’ and WP’ including
               modulation waveform modelling for selected representative modulations
WP4.4.3        Review of real time frequency management

Working Group 5 - Variability and forecasting

WP 5.1         High latitude ionospheric variability

WP 5.2         Variability statistics

WP 5.3          Disturbances

WP 5.4          Short-term forecast model

WP 5.6          Computer program




                                                        8
                Table 2 Working Group time scales

       WP          1996                     1997                     1998                    1999
WP1.1.1             |------------- ----------------------- ----------------------- ---------------------|
WP1.1.2                                    |-------------- ----------------------- ---------------------|
WP1.1.3                       |-- ---------------------- ----------------------- ---------------------|
WP1.2.1         |--------------- ---------------------- ----------------------|
WP1.2.3         |--------------- ----------------------- ----------------------- ---------------------|
WP1.3          |--------------- ---------------------- ----------------------- -----------|
WP2            |----------------- ------------------------ ------------------------ -------|
WP3.1       |----------------- ---------------------- ---------------------|
WP3.1.1     |----------------- -------------------|
WP3.1.2     |----------------- ---------------------- ---------------------|
WP3.1.3     |----------------- ---------------------- ---------------------|
WP3.1.4     |----------------- ---------------------- ---------------------|
WP3.2       |----------------- ---------------------- ----------------------- -----------|
WP3.2.1     |----------------- ----------------------- ----------------------|
WP3.2.2     |----------------- ---------------------- ----------------------|
WP3.2.3     |----------------- ---------------------- -----------|
WP3.2.4     |----------------- ---------------------- ----------------------- -----------|
WP3.3       |----------------- ---------------------- ----------------------- -----------|
WP3.3.1     |----------------- ---------------------- ----------------------- -----------|
WP3.3.2     |----------------- ---------------------- ---------------------- -----------|
WP3.3.3     |----------------- ----------------------- -----------|
WP3.4       |----------------- ---------------------- ---------------------- ----------------------|
WP3.4.1     |-----------------| ---------------------- ---------------------- ----------------------|
WP3.4.2     |----------------- ---------------------- ---------------------- ----------------------|
WP4.1.1     |----------------- ---------------------- -----|
WP4.1.3     |----------------- ---------------------- -----|
WP4.1.4     |----------------- ---------------------- -----|
WP4.2.1     |----------------- ---------------------- -----|
WP4.2.2     |----------------- ------------------|
WP4.3.1     |----------------- -----|
WP4.3.2     |----------------- -----|
WP4.3.3     |----------------- ---------------------- ---------------------- -----|
WP4.4.1     |----------------- ------------------|
WP4.4.2                                |----------------- ---------------------- -----|
WP4.4.3     |----------------- ------------------|
WP5.1       |----------------- ---------------------- ---------------------|
WP5.2       |----------------- ---------------------- ---------------------|
WP5.3       |----------------- ---------------------- ---------------------|
WP5.4                                         |------------ ---------------------|
WP5.6                                                                            |- ----|




                                            9
6.      Progress to date

        6.1 Working Group 1 Models for terrestrial systems

The purpose of WG1 is to interact with terrestrial systems users and to compare their performance data with models
results, including if possible assessment of value of real-time channel evaluation techniques and to develop new
models useful to users. Validation of the COST 238 models and maps has to be considered as a continuous process
during the collection of new measurements to store in the new data bank and also during the extension to new models
for users.


6.1.1: Data Bank

The COST 251 data bank based at the International Centre for Theoretical Physics, (ICTP) Trieste, Italy, is
operational since April 1997 from Web home page: http://www.cost251.ictp.trieste.it/. Moreover, there exists two
more Internet sites, one provided by the Rutherford Appleton Laboratory                               (RAL),     UK.
(http://rcru.te.rl.ac.uk/cost251/cost251.htm) and another provided by the Space Research Centre (SRC) in Warsaw,
Poland (Gulyaeva et al, 1997) (ftp://haydn.cbk.waw.pl/pub/idce), see §6.5.5, to allow participants and others to have
convenient access to information and to ionospheric data. The COST 251 data-base provides monthly-median and
daily hourly values of a specified ionospheric characteristic as it is measured in each of 35 European stations from
1957 to 1994 (Fig. 1). This data bank contains also TEC measurements and ionospheric absorption data.




      Figure 1. Map showing COST 251 area of Europe and locations of vertical-incidence ionosondes.

The data has also been made available to all COST 251 participants on CD-ROM from RAL. However, it should be
noted that some sets of data have still to be included in the Data Bank. Table 3 shows the stations, the data already
included in the bank and those to be included.




                                                         10
                      Table 3         COST 251 Data bank vertical-incidence ionosonde data

Station name           Geographic Geographic Data included in Data to be included         COST 251            Data included in
                        Latitude  Longitude   the COST 238     under COST 251              Data bank          COST 238 Data
                                                Data bank       Action auspices          1st June 1997        bank and not in
                                                                                                                COST 251
                             °N        °E             Years               Years              Years                 Years
Arkangelsk            64.4        40.5                             69-93            69-93
Ashkhabad             37.9        58.3                             57-99            57-94
Athens                38.0        23.6        61-87                61-89                                      61-87
Bekescaba             46.7        21.1                             64-90            64-89
Beograd               44.8        20.5        64-93                64-99                                      64-93
Budapest              47.4        19.2        67-76                57-76            57-59                     67-76
Chilton               51.5        358.7                            93-99
De Bilt               52.1        5.2         67-76                57-87            57-60,71-81               61-70
Dourbes               50.1        4.6         69-88                57-99            57-89
El Arenosillo         37.1        353.2       93-94                74-99                                      93-94
Freiburg              48.1        7.6         48-76                48-76            57-74                     48-56,75-76
Garchy                47.3        3.1         61-73                61-73                                      61-73
Gibilmanna            37.6        14.0        76-91                76-99            76-94
Gorki                 56.1        44.2                             58-91,92*        58-88,89*,92*
Istanbul              41.1        29.0        93-94                93-94                                      93-94
Juliusruh             54.6        13.4        61-93                57-99            57-94
Kaliningrad           54.7        20.6        64-93                64-99            64-94
Kiev                  50.5        35.5        64-92                64-99            64-92
Kiruna                67.8        20.4                             57-99            57-70,72-78,80-86,91-94
Lannion               48.7        356.6       71-93                71-99            71-89                     90-93
Lerwick               60.1        358.8                            93-99
Lindau                51.6        10.1        64-76                64-79            70-79                     64-69
Lisbon                38.8        350.8       87-92                87-92            87-89                     90-92
Loparskaya            68.0        33.0                             57-99            57-77,81-94
Lycksele              64.6        18.8                             57-99            57-78,80-94
Miedzeszyn (Warsaw)   52.2        21.2        60-85                58-99            58-85
Moscow                55.5        37.3                             45-99            57-94
Murmansk              69.0        33.0                             57-86
Nikosia               35.1        33.2                             90-99
Nurmijarvi            60.5        24.6                             57*,58-87        57*,58-87
Poitiers              46.6        0.3         57-94                57-99            57-89,92*                 90-94
Pruhonice             50.0        14.6        58-93                58-99            58-79                     80-93
Rome                  41.9        12.5        49-91                49-99            58-94                     49-57
Rostov                47.2        39.7                             49-94            57*,58-80,91-94
Slough                51.5        359.4       67-90                31-95            57*,58-94
Sodankyla             67.3        26.6                             57-99            57-89
Sofia                 42.7        23.4        64-94                62-99            64-74                     75-94
South Uist            57.4        7.3         85-89                69-90            85-89
St Peter Ording       54.3        8.6         83-91                83-91,92*        83-92,92*
St Petersburg         59.9        30.7                             49-99            57-94
Sverdlovsk            56.4        58.6                             57-99            57-94
Tbilisi               41.7        44.8                             63-86            63-86
Tortosa               40.8        0.5         68-93                57-99                                      68-93
Tromso                69.7        19.0                             57-78            58*
Uppsala               59.8        17.6        65-92                57-99            57-94
Station-years                                 570                  1421             911                       213
Stations                                      26                   45               36                        16
                                              40%                                   64%                       15%

* only a few months available
During the 5th MC meeting it was decided to set up a quality control team to check up quality and reliability of the
stored data (e.g. D. Buresova, 1997).




                                                              11
6.1.2: Oblique sounding and short-term vertical measurements

Oblique sounding and short-term vertical measurements have been made (Levy and Bamford, 1997, Jodogne et al.,
1997) which allow to obtain experimental profiles to compare them with models.


6.1.3: Single Station Models (SSM)

An important work has been accomplished by increasing the number of single station models. New models have been
developed ((I)Stanislawska and Juchnikowski, 1996; (II) Pancheva and Mukhtarov, 1996; (III) Xenos et al., 1996;
1997; (IV) SolŠ, 1997) and compared with that of COST 238 and other currently available internationally models
(Table 4). The new models seem to be very promising (Alberca et al., 1997).


6.1.4: Profile and Models

Several groups have been working on vertical electron density profiles (Cander et al, 1996). Comparisons of height
profiles obtained by different methods have been made and the results have been presented and discussed.


6.1.5: Target ranging and location

The objectives is to evaluate the usefulness of the COST 238 ionospheric models for an operational system. Thus,
monthly median and instantaneous profiles have been produced from these models for several days for which oblique
soundings between Lannion and Toulon were available. Ray tracing was performed and the results were compared
with oblique measurements (Bourdillon et al., 1997).

Arrangements had been made for data collection for target ranging. A minimum criteria for synchronisation and
resolution were defined.

Several pre-recorded data sets have been found to meet the campaign criteria:

• A path between Norway and UK in November 1988
• A path between Italy and France in December 1991
• Various paths with Sweden in 1989.

The effect of short term (15 min) variations of the vertical profile on oblique path range measurements has been
modelled.




                                                         12
Table 4 Standard deviation in MHz and average value of percentage deviation of the different models (from
Alberca et al., 1997).

                                    standard
    Stations                        deviation                    average %
                        Model I       Model II     Model III       Model IV       PRIME/        IRI 95
                                                                                   UIT-R
     Arkangelsk       0.38          0.37          0.40           0.26          0.63           0.60
        69-93                6.47          6.72           6.73          5.09          10.06           9.95
     Ashkhabad        0.44          0.40          0.40           0.29          0.62           0.69
    57-62, 64-94             4.70          4.63           4.56          3.57           6.49           7.69
       Dourbes        0.39          0.34          0.38           0.22          0.44           0.54
        57-89                5.17          4.80           5.01          3.16           5.26           6.87
    El Arenosillo     0.73          0.58          0.48           0.25          0.81           0.79
        74-85                8.34          6.37           5.64          3.46           9.45           9.33
        Ebro          0.54          0.41          0.49           0.29          0.56           0.63
        55-86                5.99          5.01           5.22          3.58           5.38           7.03
     Gibilmanna       0.48          0.40                         0.33          0.56           0.64
        76-80                6.04          5.02                         4.31           7.48          10.23
      Juliusruh       0.38          0.37          0.39           0.24          0.43           0.60
        57-94                5.31          5.25           5.63          3.57           5.55           7.58
     Kaliningrad      0.38          0.36          0.38           0.22          0.41           0.56
        64-94                5.46          5.21           5.37          3.44           5.52           7.44
        Kiev          0.38          0.34          0.38           0.22          0.43           0.56
    64-76, 78-92             4.79          4.64           4.94          3.11           5.35           7.14
       Kiruna
    57-62, 64-86,     0.46          0.41          0.67           0.33          0.66           0.65
        91-94                7.21          6.83           9.94          6.12          10.02          10.20
      Leningrad       0.39          0.37          0.40           0.27          0.61           0.60
    57-88, 91-94             6.09          5.78           6.09          4.50           9.69           9.54
     Loparskaya
 57-62,64-77,81-84,   0.39          0.40          0.70           0.28          0.62           0.65
      86, 89-94              5.68          6.30           9.84          4.73          10.83          10.97
      Lycksele        0.44          0.41          0.43           0.31          0.61           0.61
    64-76, 78-92             7.27          7.16           7.47          5.81           9.73           9.48
       Moscow         0.41          0.38          0.40           0.26          0.59           0.63
        57-94                5.58          5.20           5.56          3.76           7.81           7.86
       Poitiers       0.41          0.36          0.38           0.23          0.50           0.58
        64-92                4.84          4.51           4.76          2.97           6.57           7.37
      Pruhonice       0.44          0.33          0.35           0.33          0.47           0.53
        58-79                5.23          4.68           4.98          4.31           5.64           6.83
        Rome          0.46          0.39          0.46           0.25          0.53           0.58
        76-90                4.71          4.44           4.71          2.77           5.19           6.42
       Rostov         0.48          0.34          0.35           0.30          0.66           0.59
    57-80, 91-94             5.15          4.34           4.37          3.63           6.55           7.04
       Slough         0.43          0.37          0.39           0.24          0.45           0.56
        54-89                5.62          5.09           5.36          3.39           5.50           7.22
        Sofia         0.53          0.41          0.51           0.39          0.69           0.74
        62-93                6.11          5.35           6.13          4.99           7.37           8.56
     Sverdlovsk       0.40          0.38          0.39           0.28          0.62           0.65
        57-94                5.61          5.24           5.54          4.14           8.81           8.26
       Uppsala        0.46          0.40          0.43           0.32          0.65           0.68
    57-89, 91-94             7.15          6.35           6.42          5.46          10.05          10.37

                                                     13
        6.2 Working Group 2 Models for Earth-space systems

During the second year of COST 251 Working Group 2 continued with the various tasks listed in the adopted Work
Plan. No completion of tasks was planned but work on several subjects made good progress.

During the report time interval emphasis was on two subject groups:
a) assessment of the data situation;
b) extension of the mapping area from COST 238 to COST 251.

(a) Assessment of the data situation

One of the ‘ classical’ sources of TEC data, the signals of the (US) Navy Navigation Satellite System (NNSS), is still
usable over Europe but with degraded temporal resolution. (NNSS has been decommissioned as a navigation system at
the 31st of December, 1996 but 6 satellites continue to transmit coherent 150/400 MHz signals). In the frame of COST
251 NNSS derived TEC data are very important for three purposes: assessment of TEC maps, comparison of NNSS--
TEC with GPS--TEC (see below), ionospheric tomography (see below). To our knowledge four institutions are
involved in continuous collection of NNSS data: IROE Firenze with two receivers, the University of Graz, the Max-
Planck-Institute for Aeronomy and DLR/DFD Neustrelitz with one receiver each. The research group at the University
of Aberystwyth operates a number of NNSS receivers in its tomography campaigns (see below).

The WG 2 contribution to the COST 251 Workshop in Prague concentrated on Novel Data Sources not only because of
the importance of this topic to WG2 but because the members of the Working Group are convinced that a strong
impact on the work of the other groups is very likely. We refer to the Workshop Proceedings (Leitinger et al, 1996a,
COST251TD(96)017) but point here to developments.

(1) There is no doubt that already now the most important source of satellite to ground total electron content data are
    ‘geodetic’ receivers for the signals of the (US) Global Positioning System (GPS). So far the Russian equivalent
    (GLONASS) has not found much use in Western Europe but since the inclination of the GLONASS satellites is
    higher (62 degrees - GPS: 55 degrees) the use of GLONASS signals to gain ground based TEC would be very
    valuable for COST 251. Use of Global Navigation Satellite Systems (GNSS - presently GPS and GLONASS) has
    changed TEC acquisition radically. With the ‘   old’ data sources (VHF beacons on geostationary satellites used for
    ‘Faraday’ observations; VHF/UHF coherent signals on low orbiting navigation satellites for ‘             Differential
    Doppler’ observation) the ionospheric observatories used their own dedicated receivers and data treatment
    (retrieval, evaluation, storage). GNSS data are gained in cooperative efforts by satellite geodesy oriented research
    groups and are stored centrally. The most important data collection is that of the International GPS Service for
    Geodynamics (IGS) (see, e.g., IGS Directory 1997). The IGS data collection consists of raw data from which
    electron content can be derived by two methods, namely Group Delay (plasma influence on modulation phase)
    and Differential Doppler (plasma influence on carrier phase). In principle, Group Delay provides ‘    absolute’ TEC
    with inherent inaccuracies due to inaccuracies and fluctuations in transmitter and receiver delays and to phase
    noise. Differential Doppler needs external data for ‘ calibration’ (to find a value for the unknown ‘  initial value’
    which can be considered as an integration constant) but gives much better (temporal and spatial) TEC resolution
    than Group Delay. The best solution seems to be the combination of Group Delay with Differential Doppler data.
    Several approaches are in discussion which differ by the number of receiving stations used and by the application
    purpose of the TEC data. Details will be given in a report. The foundations for it were laid during the joint
    COST251/IRI Workshop at Kühlungsborn and during a GPS/Ionosphere Workshop and WG2 ‘                 Group Meeting’
    held at the University of Graz in the end of June.

In the frame of COST 251 electron content data are used for ‘long term’ and ‘instantaneous’ applications. In the ‘long
term’domain we mention the following main purposes:

(1) validation of the COST 238 TEC map,
(2) construction and testing of the COST 251 TEC map,
(3) construction of the COST 251 median electron density profile.

‘Instantaneous’applications are among others:



                                                          14
(1) construction and test of instantaneous mapping procedures (nowcasting) of electron content,
(2) interchange of TEC with foF2 data in instantaneous mapping applications,
(3) updating of regional models. Figure 2 shows an example for the latter application: hourly maps of TEC from the
    regional TEC model of DLR Neustrelitz, updated with TEC from several European GPS receiving stations.

In the frame of COST 251 the research group at DLR/DFD Neustrelitz (led by N. Jakowski) is presently the most
active one in deriving TEC from GPS and in assessing relevant data (Jakowski, 1996; Jakowski and Sardon, 1996;
Jakowski et al 1996a, b, c; Jakowski et al, 1997a, b). The following list contains some details of the relevant work
done at Neustrelitz:

−   Continuation of GPS measurements in DLR/DFD Neustrelitz on a routine basis
−   Derivation of TEC of the ionosphere from GPS measurements including a number of European GPS tracking
    stations of the International GPS Service for Geodynamics
−   Evaluation of the accuracy of the derived vertical TEC data products by comparisons with vertical sounding
    (bottomside and topside), incoherent scatter radar and altimeter measurements
−   Improvement of the European TEC model NTCM1 by it's newer version NTCM 2
−   Construction of TEC maps over Europe on a routine base (hourly plots available under http://www.nz.dlr.de/gps)
−   Comparison of the GPS-derived TEC data with model data such as IRI90, IRI95 and Bent
−   Computation of monthly median TEC maps over Europe
−   Preparation of the corresponding data files for the COST 251 data bank at the ICTP in Trieste according to the
    COST standard format
−   Delivery of monthly median TEC maps over Europe derived for 1995 to the COST 251 data bank in July 1997
−   Further studies were related to:

• Relationships of TEC with solar activity, season and geomagnetic activity
• Derivation of the ionospheric slab thickness by comparing GPS and vertical sounding data and related conclusions
  to the COST 238 electron density profile
• Conclusions for ionospheric correction application tasks in space based radio navigation systems
• Ionospheric corrections in GPS radio occultation measurement systems

Other GPS related activities which fit into the COST 251 Action have been reported from IROE Firenze (GPS
accuracy assessments, GPS -- NNSS comparisons, P. Spalla and L. Ciraolo (see Ciraolo and Spalla, 1997)), and from
the Royal Observatory of Belgium (R. Warnant, extensive GPS accuracy assessments (see Warnant, 1996)) and the
Royal Meteorological Institute of Belgium (J.-C. Jodogne, comparisons of GPS--TEC with TEC derived from
ionosonde data (see Leitinger et al, 1996a)).




                                                        15
Figure 2 :   Example for the Neustrelitz Regional TEC Model NTCM2 updated with GPS data. 2 February 1


                                                           16
(2) Ionospheric tomography is a novel application of TEC data gained by means of the Differential Doppler effect on
    the signals of the (US) Navy Navigation Satellite System (NNSS). Tomographic reconstruction needs data from
    meridionally aligned chains of NNSS receivers. There is no doubt that ionospheric tomography has reached the
    production stage in higher latitudes where ionospheric structures are rather strong. The results are two
    dimensional electron density profiles (height as the vertical coordinate, geographic latitude as the horizontal
    coordinate) (Leitinger, 1996; Leitinger and Kirchengast, 1996; Rothleitner et al, 1996; Leitinger et al, 1996b). In
    the frame of COST 251 tomographic reconstruction is especially valuable for studying the main trough of the F
    layer. Figure 3 contains a good example of the trough with EISCAT verification.

     In the frame of COST 251 the research group at the University of Aberystwyth is presently the most active one in
     producing relevant tomography results from campaigns carried out in Northern Europe (Kersley et al, 1996;
     1997; Mitchell et al, 1997; Pryse et al, 1996; Walker et al, 1996).

(3) GPS (GLONASS) receivers onboard of low orbiting (LEO) satellites provide the possibility to observe the
    occultation of the signals by the surface of the earth. One receiver (GPS/Met) is on the small research satellite
    MicroLab 1. It provided setting occultation data. Inversion of the data give horizontally averaged height profiles
    of electron density from around 80 km to the height of MicroLab 1 (about 740 km). Figure 4 shows an example
    for such a profile. Model calculations have shown that inversion profiles from the COST 251 area are
    representative and give excellent height of the F2 layer peak. Combination with ground based data (electron
    content from NNSS or from dense networks of GPS/GLONASS receivers) can lead to tomographic reconstruction
    possibilities preserving the excellent height information of the occultation data and the horizontal resolution of
    the ground based TEC data.

Extensive assessment studies are carried out at the University of Graz (Leitinger et al, 1997a, b).

(b) Extension of the Mapping Area

For TEC mapping the eastward extension of the Mapping Area poses a data problem: up to now no TEC data have
surfaced for the region east of the COST 238 area. However, WG 2 expects no major problems because both empirical
and theoretical assessments have shown that the extension can make use of experiences gained with F2 layer peak
density (Nmax). From present knowledge WG 2 expects that it will be necessary to decide between two options: TEC
mapping in geographic latitude and local time (no true longitude dependence) or TEC mapping in geomagnetic
latitude and local time. The first option would mean to apply a COST 238 type map to the wider COST 251 area.

The poleward extension of the mapping area will need a new philosophy.

Two important conclusions could be adopted:
(1) monthly median mapping of ionospheric electron content (TEC) makes no sense poleward of the minimum of the
    main trough;
(2) trough region modelling is not compatible with the classical approach but needs a magnetic activity parameter as
    additional input.

The first conclusion means dynamic application borders for the COST 251 monthly median maps (at least border
dependence on local time and on a magnetic activity parameter). The second conclusion needs a decision on a suitable
additional input parameter. Since the trough is a rather small scale feature in latitude it will be necessary to use
superposition of a trough model on a classical monthly median TEC map.

Trough modelling should be done in cooperation with the other Working Groups of the COST 251 Action. W G 2 will
provide data and experience from TEC evaluation but a uniform product needs agreement on procedures and decisions
of the Management Committee.




                                                           17
Figure 3: Example for the tomographic reconstruction of trough region electron densities (top) and EISCAT
          verification (bottom). For a detailed description see COST251TD(96)017.




                                                      18
Figure 4:          Example for the inversion of GPS/MET phase difference data (top), occultation on 22 Oct., 1995,
            07:34:51 UT. Resulting electron density profile (no post-processing) in the bottom. Ground point of
                                  N,
            occultation ray: 34.2° 20.7° E.




                                                          19
        6.3 Working Group 3 Ionospheric modelling

6.3.1: Monthly median mapping

6.3.1.1 New indices of ionospheric state

A statistical analysis of hourly monthly median foF2 values from different COST 251 stations and corresponding
values of a new ionospheric index of state of solar-cycle variation is carried out with the purpose to improve monthly
median analytical models and thus ionospheric prediction (Papandoniou et al., 1997). The results are then compared
with similar results obtained when other indices (e.g., R12, T12 and MF2) are used.

Long-term prediction of the monthly index MF2 values is based on prediction of R12. Then using this R12 a monthly
MF2 index forecast is produced. The MF2 forecast consists of two parts: 1) long-term prediction of MF2_12 and 2)
calculation monthly MF2 using this MF2_12. An analysis of the MF2_12 versus R12 regression for 50 years shows
that to be quite an acceptable: SD=0.21-0.23 and relative mean deviation 2-2.2% if consider the rising phase of solar
cycles separately, or for the whole cycles without separation for rising and falling phases. Then a real accuracy of
monthly MF2 determination has been checked. In the retrospective mode when observed R12 are used, the accuracy of
getting monthly MF2 is 6-10%. The best results - during summer period (from May to Sep - around 6%), to the worst
- in equinox (Feb, Mar, Apr, Oct, Nov - about 8-10%), winter period -about 8%. In principle, this looks as acceptable
keeping in mind very close foF2 with MF2 relation.

6.3.1.2 Long-term trends of ionospheric change

The investigations of long-term trends in ionospheric data series have been continued with foF2 and hmF2
observations of 11 different European ionosonde stations (Bremer, 1996a). The foF2 and hmF2 trend coefficients are
relatively small, positive as well as negative. There is no detectable dependence on latitude for both parameters.
Putting all monthly trend parameters together a small seasonal variation of the foF2 trend remains with slightly
positive values in winter and negative values in summer and a yearly mean value of : -0.0015 MHz/year. The mean
hmF2 trend has no clear seasonal variation and a yearly mean value of : -0.11 km/year.

Long-term trends in the upper middle atmosphere as detected by ionospheric measurements have been actively studied
(Bremer, 1997; Bremer et al., 1997; Lastovicka 1996a) .

6.3.1.3 Monthly-median mapping techniques

An improved version of monthly median foF2 and M(3000)F2 ionospheric model, MQMF2-02 is developed for COST
251 area (Mikhailov and Mikhailov, 1997). A new set of ionosondes including high-latitude and east-European ones is
used for model derivation. The model is based on the multiquadric method of spatial interpolation and an improved
ionospheric index MF2-02. A non-linear dependence of foF2 and M(3000)F2 on solar activity level, expressed by
MF-02 index, is used to establish local models for each ionosonde station. Outside the COST 251 area the model
smoothly interfaces to the global ITU-R model.

A regional ionospheric model of the standard median ionospheric characteristics has been recently evolved from the
SIRM (Simplified Ionospheric Regional Model) model for applications in a more extended area, taking into account
the consequences of high latitude behaviour and of longitudinal effects. The model, an improvement of SIRM studied
for the European area and then applied also in other mid latitude regions is based on the Fourier coefficients
calculated month by month, coming from the analysis of the median monthly values of the ionospheric parameters
measured in the stations of the European and near east region under the COST 251 Action (Zolesi et al., 1997). At
this preliminary stage the new model gives very satisfying results during summer months, although it still presents
important differences during winter at latitudes greater than 55 degrees. In Figure 5 it is shown an example of the
improved SIRM for Poitiers station giving the comparison of the diurnal monthly median behaviour of foF2 predicted
by the model and the real median hourly values measured at the station in January 1983.




                                                         20
                                 10.00                MHz

                                                        measured
                                                                                                                                  foF2


                                                       Impr. SIRM
                                   5.00
                                                                                            Poitiers

                                                                                   January 1983 R12 = 93


                                                                                                                                                              U.T.
                                   0.00

                                            0.00                 5.00              10.00                 15.00                        20.00                       25.00

Figure 5: Comparison of the diurnal monthly median behaviour of foF2 for January 1983 predicted by the improved
          SIRM (dotted line) and measured at Poitiers (continuous line) .

A study of a probability function for the occurrence of F1 ledge and L condition was been continued involving the
expression :
                               P(χ,λ ,R12)=[0.5 + 0.5 cos (χ)],

where λ is the geomagnetic latitude, χ the solar zenith angle and γ numerical exponent. The coefficients were
                                                                      a
calculated using data base of 22 years from 1969 to 1990 (Scotto et al., 1997). For the case of F1 ledge and L
                                    ≈
conditions together it is obtained γ 2.36 without significant dependence on R12 and λ Preliminary analysis of data
                                                                                     .
show that this formula can be still improved, considering the dependence from the geomagnetic latitude, while the
independence of the probability of occurrence form R12 can be retained. Also an improved smoothed probability
function can be obtained and tested by an independent base of data.

6.3.1.4 New procedure

A study has been focused on the development of the monthly median ionospheric frequencies model by using different
neural networks (Cander and Lamming, 1997). Figure 6 illustrates an example of the results obtained with time series
prediction neural network model and compared with observations at Poitiers ionospheric station. The agreement
between predicted and observed values is excellent at all levels of solar activity (Lamming and Cander, 1997).

                                                                                                                  R12            foF2 observed             foF2 predicted
                                 140




                                 120




                                 100
          foF2 (*0.1MHz) / R12




                                  80




                                  60




                                  40




                                  20




                                   0
                                       88




                                                 88




                                                            88




                                                                     88




                                                                              88




                                                                                       88




                                                                                                   88




                                                                                                             88




                                                                                                                            88




                                                                                                                                     10
                                                                                                                                          88




                                                                                                                                                 11
                                                                                                                                                      88




                                                                                                                                                             12
                                                                                                                                                                  88
                                   1




                                             2




                                                        3




                                                                 4




                                                                          5




                                                                                   6




                                                                                               7




                                                                                                         8




                                                                                                                        9




                                                                                            Month/Year



Figure 6: Time series neural netvork predicted and observed foF2 values during 1988 at Poitiers ionospheric station.




                                                                                             21
6.3.1.5 Testing development

Long-term mapping testing procedure has been proposed by Cander et al., (1997) and discussed. Final decision has
not jet been made.

6.3.2: Instantaneous mapping

6.3.2.1 Instantaneous mapping applications


Instantaneous mapping is defined as the technique that is applied when simultaneously measured or forecast values of
ionospheric characteristics at limited numbers of locations are used for map generation appropriate to a single moment of
time. Generally the number of measurement locations is insufficient for the production of fully accurate maps, even over a
restricted geographical region, and use must be made of artificial screen-point values to constrain the mapping contours in
remote areas. Higher latitudes are significantly influenced by the mid-latitude trough by night and because of a range of
longitudes there are additional changes to those associated with the varying local time. In this situation a modified kriging
mapping technique is proposed be applied to available measurements, together with additional values defined by SSM's for
                                                                                                 s,
some locations and also incorporating a new mid-latitude trough model. Mapped area with SSM’ bound-point positions and
trough model are shown at Figure 7.




Figure 7: Mapped area showing locations with SSM's (crosses) and bound-point positions (squares). The trough region
model is illustrated (shaded) for local magnetic midnight at 30°E with index Kp* = 4.

In an application all available measurements are used as input data, with no required minimum number for the mapping to
proceed. These are supplemented by other input data taken from the SSM's for all available locations for which there are no
measurements available for the epoch under consideration (Alberca et al., 1997).

Further map input data are taken at 12 uniformly separated positions (bound points) around the perimeter of the designated
area being mapped not near SSM locations (see Figure 7). For these points, values are given in terms of smoothed sunspot
number R12 by monthly median empirical formulations as recommended in the PRIME are smoothly interfaced to world-
wide ITU-R models via a uniform 5° wide buffer zone. Kriging is not applied directly to the data values thereby deduced but
to the differences with respect to the PRIME mapped figures, ie with the bound points all being zero. Stanislawska and
Juchnikowski (1997) have shown this to be a superior technique which smoothes out discontinuities. Afterwards all values are
denormalised to their true dimensions.

The latitude of the trough minimum at the layer peak height, expressed in invariant coordinates, is adopted from the model of
Karpachev and Deminov (1997) based on COSMOS-900 and INTERCOSMOS-19 satellite data for the northern hemisphere.
As well as moving equatorwards, the trough is known to broaden and become more prominent with increasing magnetic

                                                             22
activity. These have involved treating the depth as a fractional departure or as a linear reduction from the no-trough case,
depending on the value of Kp*. The model adopted, based on foF2 values derived from analyses of MAGION-3 HF radio
spectrometer data (Rothkaehl et al., 1997), gives a linear reduction of frequency that has a bi-Gaussian latitudinal
dependence with a sharp equatorwards variation from the minimum and a more gradual recovery polewards, except for very
high levels of magnetic activity when it is taken to be parabolic in form with equally broad latitudinal changes either side of
the trough minimum. For other than midnight a recovery from the trough minimum proportional to cos (c) (zenith angle) is
introduced.

An example of an instantaneous foF2 map created by the above technique for 10 May 1992 at 22 UT during an intense
magnetic storm is presented in Figure 8.




Figure 8: Sample instantaneous map of foF2 (x10/MHz) for 10 May 1992 at 22 UT with Kp*=7 given by the new
model with five measurements.

An instantaneous mapping technique has been used for other applications also for studying the ionospheric disturbances
behaviour. The penetration of ionospheric disturbances in European sector has been shown by Kutiev et al., (1997).

6.3.2.2 Screen-point locations and values specifications

An important role of defining quiet and disturbed ionospheric conditions has been shown by Bilge et al., (1997). The separate
representation for storm and quiet conditions is planned. The first part - ‘ QUIET CONDITIONS’ foF2 modelling is a two
stage process. First an average foF2 is produced over all hours for each month, station and year. Then a linear dependence to
such values with R12 to establish a solar-cycle law for each month and each station separately is fitted. Then in turn a linear
dependence with latitude to the two constants of this law for each month and each station is produced. This becomes the
first-order model to describe the principal latitudinal, seasonal and solar-cycle changes. Returning to the individual station
measurement data the model values are subtracted and the month-to-month and within-a-month temporal changes are
examined, thereby finding the various periodicities. The model approximates the data with 6% error (Figure 9). This error is
mainly due to inadequate modelling of foF2 dependence on R12, the well known hysterisis effect. The 6% error figure can be
improved by using the rising or falling position of each solar cycle only.




                                                              23
Figure 9: Total power of the residual term per the total power of the observed foF2 value for each station between 1970 and
          1989

6.3.3: Electron density height profile

6.3.3.1 Development of model

The PRIME D-region electron density model, based on rocket-borne probe measurements and the statistical D-region
model FIRI02, based on rocket-borne radio wave propagation measurements (Friedrich and Torkar, 1997) have been
tested with experimental radio wave propagation data in the LF range. Radio wave reflection coefficients are
calculated for both models using the full-wave method and compared with radio wave absorption data in the
frequency range 50 to 45 kHz obtained in a long term observational program in Middle Europe. The diurnal and
seasonal variation and the dependence on solar activity are investigated. The diurnal variation of the experimental
absorption data in summer at low solar activity is well reproduced by the PRIME model for solar zenith angles less
than 80 degrees and by the FIRI02 model for solar zenith angles greater than 40 degrees. The seasonal variation at low
solar activity is well described by both models with the following exceptions: the PRIME models provides too high
absorption values in winter and the FIRI02 model too high values in spring. The solar activity dependence is
investigated in summer at a solar zenith angle of 60 degree, the PRIME model is in good agreement with the
experimental data whereas the FIRI02 model gives too high absorption values at high solar activity (R12=100) as it is
shown by Singer (1997).


6.3.3.2 Establishment of a data set for testing

Data sets are being implementing using the Averaged Representative Profile (ARP) procedure applied to digisonde
data.


         6.4 Working Group 4 System performance and spectrum management

Van der Perre and Van de Capelle (1996) give a short overview of the past, the present, and the future of the HF
channel simulators. Lundborg and Bröms (1996) describe the HF channel sounder DAMSON and present the results
of measurements run in northern Scandinavia. Barclay (1996) briefly reviews the current and developing techniques
for operating and planning HF systems for improved performance and quality and describes the use of ionospheric
information for such purposes.

A review on adaptive channel equalisation techniques (Arikan and Arikan, 1997a) was discussed, also calculation of
the channel scattering function from measurements (Arikan and Arikan 1997b). The resulting discussion clarified the



                                                            24
requirement for a description of this function and of the importance of the consideration of equalisation associated
with simulator design.

Theoretical calculation of the effects of ionospheric density fluctuations on the transmitted signal was achieved
(Gherm et al., 1997). This led to a preliminary discussion on the need for a comparative review of theoretical
approaches to the problem. It was generally agreed that this work can give very important contributions to the goals of
the Working Group.

Ongoing work on the effects of the antenna characteristics and results from occupancy measurements in southern
Europe were discussed (Economou et al, 1997). The results will be important for the further development of the
occupancy models

The Leeds simulator workshop (see § 4.2) report is given in COST251TD(97)003. It was reviewed by WG 4. The
International Telecommunication Union, ITU-R Study Group 9, is also studying a specification for the design and
architecture of a new high performance ionospheric simulator and liaison is being assured to avoid duplication of
effort. That Study Group is also studying new techniques for intelligent frequency adaptive systems which offer new
opportunities for major improvements in quality of service and reliability for HF communications. In the light of these
developments, of which WG 4 is fully aware, the prospects for independent fruitful research in WG 4 are now more
limited.

A new technique for single site target location by using angle of arrival for two received modes simultaneously was
discussed.

It was noted, with considerable regret, that active participation in WG 4 has significantly reduced and representatives
of only 5 countries were present at the Kühlungsborn WG 4 meetings. At Prague a large number of participants stated
that they would make contributions but these have not materialised.


        6.5 Working Group 5 Variability and forecasting

6.5.1: High latitude ionospheric variability

A new visualisation technique has been developed for studying the ionospheric variability in Europe (Pulinets, 1997).
An empirical model of the main trough has been developed (Annakuliev et al., 1997) and studies have been started to
investigate the effect of the spatial and temporal behaviour of the ionospheric trough region on HF communications
(Karpachev et al., 1996; Karpachev and Pulinets, 1996). A critical analysis of the behaviour of sporadic E-layer
variations has been initiated as it can influence HF communications at high latitude.

6.5.2: Variability statistics

Both the effect of gravity waves and quasi-periodic oscillations of 2 to 35 days have been investigated successfully to
estimate the percent contribution of these sources of variations in the inter-hourly and day-to-day variability of foF2
(Altadill, 1996; Altadill and Lastovicka, 1996; Altadill et al., 1997; Apostolov et al., 1996; Apostolov and Altadill,
1996; Boska and Lastovicka, 1996; Hanbaba, 1997; Lastovicka, 1996b; Lastovicka and Mlch, 1996; Lastovicka,
1997). A systematic analysis of the variability of the electron density at fixed heights using digisonde data and the
Averaged Representative Profile (ARP) confirms previous results and describes the variability as a function of height,
hour of day and season (Sole and Altadill, 1997). Topside electron density profile variability is being investigated
using incoherent scatter data to complement the studies done with digisonde data (Zhang and Radicella, private
communication). Additional work have been done to estimate the foF2 variability range for quiet and disturbed
conditions. Considering the relative deviations df from the median of foF2, a ‘  disturbed’ ionosphere may be defined
when df is greater than 0.3. All other periods may be considered as quiet. During quiet conditions df is not greater
than 0.2 (Kouris et al., 1996; 1997).

6.5.3: Disturbances

Disturbance effects on the behaviour of ionospheric parameters have been investigated (Bradley et al., 1997; Bremer,
1996b; Bremer, 1996c; Bremer et al., 1996; Davis et al., 1996; Fuller et al., 1997; Gordienko and Kaliev, 1997;
Kuleshova et al., 1997; Lastovicka, 1996c; Tulunay, 1996). It is found that in the European area during ionospheric
storms an average depression of foF2 could be of the order of 4 MHz, whereas an enhancement of 3 MHz (Kouris et

                                                          25
al., 1997) is observed. The reaction of the middle latitude ionosphere to geomagnetic storms has been modelled
empirically by Fourier decomposition (Kutiev and Muhtarov, 1996; Muhtarov and Kutiev, 1997) and an algorithm
based on linear prediction filters has been developed to forecast foF2 changes related to strong geomagnetic storms
(Vasilievic and Cander, 1997). An additional effect of IMF turnings on the foF2 variability has been found that can
produce an order of magnitude increase on the average departure from median conditions. When the Bz is southward
larger deviations from quiet time foF2 values (i.e., more negative dfoF2 values) may exist on the dayside when By < 0
(Figure 10).




Figure 10: The diurnal variation of δfoF2 for southward Bz (solid line); Bz and positive By (o) and Bz and
         negative
         By (x) (provided by Yurdanur Tulunay).



The ionospheric variability as quantified by the maximum change of dfoF2 turned out to be the greatest in the period
21.00-00.00-02.00 UT (or LT) for Slough foF2 data (Figure 11) (Tulunay et al., 1997). Also the Post Storm Effects
(PSE) in the D region ionisation that influences ionospheric propagated radio waves has been studied with promising
results. PSE are caused by precipitating high energetic particles during and especially after geomagnetic disturbances
and the effects can be observed in a latitudinal belt between about 40 deg and auroral latitudes on both hemispheres.
PSE are positively correlated with the geomagnetic activity level. PSE during winter are in general stronger (longer
duration) than in summer. PSE can be detected by LF absorption measurements but also observed with ionosondes
(fmin) and in HF propagation measuring paths (Bremer, 1997). Further evidences of meteorological phenomena
related changes in the electron density profile shape have been found (Boska and Knizova, 1997).




                                                         26
Figure 11: The superposed epoch analysis (spe )results of the δ     foF2 data by using the major IMF Bz soutward
         polarity changes as key dates. The δ    foF2 data are grouped in four UT(LT) sectors for the Slough
         station. In order to facilitate a comparison the spe results of the annual data are superimposed. A best
         fit to the annual spe is drawn in solid line, a best fit to the spe results of the data binned in UT(LT) is
         drawn in dotted line (provided by Yurdanur Tulunay).

6.5.4: Short-term forecast model

One-day forecasting of the ‘global’ and ‘ European’ constants have been performed for the summer months of 1981
and 1982, based on the empirical formula expressing the relative variations of foF2 as a function of the Power Index
(or Kp). The comparison with data show an acceptable agreement, with larger deviations obtained at the beginning of
the geomagnetic storms (Figure 12) (Kutiev and Muhtarov, 1996; Mutharov and Kutiev, 1997)). Short-term forecast
modelling efforts have been also oriented towards the use of neural networks for such purpose. Concrete results have
been obtained in forecasting foF2 one hour in advance by using multi-layer perceptron type of neural networks
(Altynay et al., 1997; Kumluca et al., 1997). Neural network has been also used to forecast ionospheric disturbances.




                                                         27
0.50                                Global constant

                                    European mean

                                    Prediction
0.00




                MAY 1981
-0.50

        120          240          360            480          600          720
0.50




0.00



                    JULY 1981
-0.50

        120          240          360            480          600          720
0.50




0.00



                 JULY 1982
-0.50

        120          240          360            480          600          720
0.50




0.00



                    AUGUST 1982
-0.50

        120          240          360            480          600          720

                               Hours from the beginning of the month
Figure 12: The longitudinally averaged relative foF2 (global constant - full line), European average (thin line)
           and its one-day forecast (thick line) for summer months of 1981 and 1982 (provided by Ivan Kutiev).


6.5.5: Ionospheric Despatch Centre for Europe

The Ionospheric Despatch Centre in Europe (Stanislawska, 1996; Stanislawska et al, 1997), IDCE, has been
operational since January 1997 at the Heliogeophysical Prediction Service of the Space Research Centre of PAS, the
Regional Warning Centre of the International Space Environment Service (ISES) organisation, earlier known as


                                                       28
IUWDS (International URSIGRAM and World Day Service). IDCE provides solar-geophysical data for COST 251
participants, putting stress on the ionospheric data particularly from the European ionospheric stations. Data are
available on ftp at: haydn.cbk.waw.pl, or 148.81.24.129, directory pub/IDCE. Messages are prepared on the base of 1)
local measurements, 2) daily messages from RWC' s: Meudon, Tokyo, Sydney, Boulder, Moscow, Praha, and 3)
special messages directly from the following observatories: Ondrejov, Juliusruh, Lannion, Uppsala, Tortosa, Lunping
and Sofia. Data are available from the last few days and for some days in advance, except the ionospheric data that are
collected from the whole current month.

Files available on ftp are:
• helgeo.msg - daily message containing tables: Solar Report#1-#4, magnetic activity and ionospheric disturbances;
• yymmname.ur2 - hourly ionospheric parameters for the year (yy), month (mm) from the station (name - first 4
    letters from the name of the station);
• info_dd.mm - solar-geophysical review and forecast for the day (dd) and month (mm);
• q_ d_days - catalogue of ionosphericaly quiet and disturbed days since January 1997.


7.      Acknowledgements

Acknowledgement is made to L W Barclay, Lj R Cander, G de Franceschi, S S Kouris, B Lundborg, R Leitinger, S
M Radicella, B Zolesi for provision of material included in this Report. Preparation and typing was undertaken by
Angela Vernon.

8.      References and bibliography

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                                               ,
Model for Remote Area in Instantaneous Mapping’ Acta Geophys Polonica, to be published.

                   On                                                       ,
Altadill D (1996) ‘ the 18-day quasi-periodic oscillation in the ionosphere’ Annales Geophysicae, 14, 7, 716-724.

Altadill D and Lastovicka J (1996) ‘Quasi-five- and ten-day oscillations in foF2 and their possible connection
                                               ,
with oscillations at lower ionospheric heights’ Ann Geofisica, 39, 705-712.

Altadill D, Apostolov E M and Alberca L F (1997) ‘ Some hemispheric similarities of the quasi-2-day oscillations in
         ,
the foF2’ Journal of Geophysical Research, 102, A5, 9737-9739.

Altýnay O, Tulunay E and Tulunay Y (1997) ‘Prediction of ionospheric critical frequency using neural networks’,
Geophysical Research Letter (GRL).

Annakuliev S K, Deminov M G, and Karpachev A T (1997) ‘                                                ,
                                                       Empirical formulae for the main trough position’ Joint
COST251/IRI Workshop, Kühlungsborn, Germany, 26-31 May, 1997.

Apostolov E M and Altadill D (1996) ‘   Ten periodic bands of foF2 quasi-periodic oscillations from 2 to 35 days’,
Bulgarian Geophysical Journal, 22, 3, 20-24.

Apostolov E M, Altadill D, and Alberca L F (1996) ‘Persistence of quasi-2-day oscillations in the geomagnetic activity
                        ,
indices (aN, aS and aM)’ Journal of Geomagnetism and Geoelectricity, 48, 1233-1239.

Arikan F and Arikan O (1997(a)) ‘                                               ,
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and Working Group Sessions Proceedings, (Ed: B Lundborg) Kühlungsborn, Germany, COST251TD(97)006 (Part II),
1-5.

Arikan F and Arikan O (1997(b) ‘                                                      ,
                                  Computation of scattering functions for HF channels’ Joint COST 251/IRI
Workshop and Working Group Sessions Proceedings, (Ed: B Lundborg) Kühlungsborn, Germany,
COST251TD(97)006 (Part II), 7-13.

Barclay L W (1996) ‘Operating and planning HF systems for improved performance and quality, with economical spectrum
    ,
use’ Proceedings of the First Workshop of COST 251 (Ed: J. Laštovicka), Prague, Czech Republic,
COST251TD(96)017, 142-146.


                                                          29
Bilge A H, Tulunay Y and Baykal S A (1997) ‘Theoretical spatial and temporal modelling of the COST 251 area: Quiet
           ,
conditions’ Joint COST 251/IRI Workshop and Working Group Sessions Proceedings, (Ed: A Vernon) Kühlungsborn,
Germany, COST251TD(97)006 (Part I), 37- 35.

Boska J and Lastovicka J (1996): Gravity wave activity in the lower ionosphere and in the F2 region - similarities
and differences. Advances in Space Research, 18, 3, 127-130.

Boska J and Knizova P (1997) ‘                                                                   ,
                              Changes in N(h)-profiles connected with strong tropospheric events’ Joint COST
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COST251TD(97)006 (Part I), 59-62.

Bourdillon A, De Franceschi G, Zolesi B and Le Roux Y (1997): ‘Use of the PRIME vertical profiles for ray-tracing
                                       ,
and comparison with oblique soundings’ Joint COST 251/IRI Workshop and Working Group Sessions Proceedings,
(Ed: A Vernon) Kühlungsborn, Germany, COST251TD(97)006 (Part I), 14-20.

Bremer J (1996a) ‘                                                                                 ,
                  Some additional results of long-term trends in vertical-incidence ionosonde data’ COST
251TD(96)025.

Bremer J (1996b) ‘The mean solar magnetic field as an indicator of the inter-planetary magnetic field’ Ann Geofisica,
39, 713-720.

Bremer J (1996c) ‘                                                                     ,
                  The influence of high speed plasma streams on the ionospheric plasma’ J Atmos Terr Phys, 58,
845-854.

Bremer J (1997) ‘                                               ,
                 Long-term trends in the meso- and thermosphere’ Advances in Space Research, to be published.

Bremer J, Lastovicka J and Tulunay Y (1996) ‘ Influence of the interplanetary magnetic field on the variability of
                          ,
the mid-latitude F2-layer’ Ann Geofisica, 39, 721-727.

Bremer J, Schminder R, Greisiger K M, Hoffmann P, Kuerschner D and Singer W (1997) ‘       Solar cycle dependence
                                                                            ,
and long term trends in the wind field of the mesosphere/lower thermosphere’ J Atmos Solar-Terr Phys 59, 497-509.

Buresova D (1997) ‘                                           ,
                   Results of foF2 testing with UNDIV program’ Studia Geoph et Geod, 41, 82-87.

Cander Lj R, Jodogne J-C, Kutiev I, Levy M F and Mukhtarov P (1996) ‘Profile models validation: A view on PRIME
                              ,
N(h) model present and future’ 4-14.

Cander Lj R and Lamming X (1997) ‘        Neural networks in ionospheric prediction and short-term forecasting’ 10th
                                                                                                               ,
International Conference on Antennas and Propagation, IEE Conference Publication, 436, 2.27-2.30.

Cander, Lj R, Hanbaba R and Zolesi B (1997) ‘                                     ,
                                             Long-term mapping testing procedures’ Presentation at the Working
Group Sessions of COST251, Kühlungsborn, Germany, 26-31 May 1997.

Ciraolo L and Spalla P (1997) ‘Comparison of ionospheric total electron content from the Navy Navigation Satellite
                    ,
System and the GPS’ Radio Science, 32, to be published.

Davis C J, Wild M N, Lockwood M and Tulunay Y (1997) ‘   Ionospheric and geomagnetic responses to changes in
                                 ,
IMF Bz :A Superposed Epoch Study’ Annales Geophys, 15, 217-230.

Economou L V, Pantjiaros C A, Gott G F, Laycock P J and Broms M (1997) ‘   The effect of the antenna on the
                                     ,
measurement of HF spectral occupancy’ Joint COST 251/IRI Workshop and Working Group Sessions Proceedings,
(Ed: B Lundborg) Kühlungsborn, Germany, COST251TD(97)006 (Part II), 27-39.

Friedrich M and Torkar K M (1997) ‘    Comparison between a statistical and a chemical model of the D-region’,
Advances in Space Research, to be published.

Fuller - Rowell T J, Codrescu M V, Araujo-Pradere E and Kutiev I (1997) ‘ Progress in developing a storm-time
                             ,
ionospheric correction model’ Joint COST251/IRI Workshop, Kühlungsborn, Germany, 26-31 May, 1997.




                                                         30
Gherm V E, Zernov N N and Lundborg B (1997) ‘   Coherence, correlation and scattering function of HF fields in the
                       ,
fluctuating ionosphere’ Joint COST 251/IRI Workshop and Working Group Sessions Proceedings, (Ed: B Lundborg)
Kühlungsborn, Germany, COST251TD(97)006 Part II, 41-57.

                                   On                                                ,
Gordienko G and Kaliev M Z (1997) ‘ methods for analysis of ionospheric disturbances’ Poster presentation at
Joint COST251/IRI Workshop, Kühlungsborn, Germany, 26-31 May, 1997.

Gulyaeva T, Stanislawska I, Alberca L F, Bremer J, Broms M, Cannon P, Hanbaba R, Jodogne J-C, Juchnikowski G,
Lyser Th, Levy M F, Milodrowska M, de la Morena B, Radicella S M and Tulunay Y (1997) ‘       Current status and
                                                                           ,
prospects of daily exchange of the Ionospheric data and forecasts via IDCE’ COST241TD(97)004.

Hanbaba R (1997) ‘Introduction of the relative variability of foF2 about the monthly median in COST251 models’,
Working Group Sessions of COST251, Kühlungsborn, Germany, 26-31 May, 1997.

Jakowski N (1996) ‘                                                        ,
                     TEC Monitoring by Using Satellite Positioning Systems’ Modern Ionospheric Science (Eds: H.
Kohl, R. Ruester, K. Schlegel) ProduServ GmbH Verlagsservice, Berlin, 371-390.

Jakowski N and Sardon E (1996) ‘     Comparison of GPS/IGS derived TEC data with parameters measured by
                                           ,
independent ionospheric probing techniques’ Proceedings of the 1996 IGS Analysis Center Workshop, Silver Spring,
USA, 19-21 March, 1996.

Jakowski N, Sardon E, Engler E, Jungstand A and Klaehn D (1996a) ‘        About the use of GPS Measurements for
                                                                                              ,
Ionospheric Studies, GPS Trends in precise Terrestrial, Airborne, and Spaceborne Applications’ IAG Symposium Nr.
115, (Eds: Beutler, Hein, Melbourne, Seeber), Springer-Verlag Berlin Heidelberg, 248-252.

Jakowski N, Sardon E, Engler E, Jungstand A and Klaehn D (1996b) ‘Relationships between GPS-signal propagation
                               ,
errors and EISCAT observations’ Ann. Geophysicae 14,1429-1436.

                                                A                                            ,
Jakowski N, Sardon E and Schlueter S (1996c) ‘ European TEC model based on GPS-Measurements’ paper
presented at the XXVth General Assembly of URSI, Lille, France, 28 August-5 September, 1996.

Jakowski N, Sardon E and Schlueter S (1997a) ‘                                                         ,
                                              Comparison of a GPS-based European TEC model with IRI 95’ Joint
COST 251/IRI Workshop and Working Group Sessions Proceedings, (Ed: A Vernon) Kühlungsborn, Germany,
COST251TD(97)006 (Part I), 21-29.

Jakowski N, Kugland H-G, Schlueter S, Rios V H, Inzirillo R and Leitinger R (1997b) ‘Latitudinal TEC profiles over
                                                                                           ,
Argentina based on NNSS Differential Doppler measurements during the period 1994-1996’ paper presented at the
Beacon Satellite Symposium, Sopron, Hungary, 30 June-5 July, 1997.

Jodogne J-C, Alberca L F and de la Morena B (1997) ‘ Oblique incidence sounding between Belgium and Spain using
                                                            ,
the phase information to improve the time delay measurement’ Presentation at the Working Group Sessions of COST
251 Kühlungsborn, Germany.

Karpachev A T, Deminov M G, Annakuliev S K, Afonin V V and Smilauer Y (1996) ‘Statistical characteristics of
different ionospheric troughs on longitude, local time, season, storm phase and geomagnetic indices’       ,
COST251TD(96)032, a review, Working Group Sessions of COST251, Prague, Czech Republic, 24-28 September
1996.

Karpachev A T and Pulinets S A (1996) ‘Model presentation of F2 layer characteristics (N T NF2 hF2) in the vicinity
                ,
of main trough’ COST251TD(96)033, Working Group Sessions of COST251, Prague, Czech Republic, 24-28
September 1996.

Karpachev A T and Deminov M G (1997) ‘Model of the Mid-latitude Ionospheric Trough on the Base of COSMOS-900 and
                               ,
INTERCOSMOS-19 Satellites Data’ Advances in Space Research, to be published.

Kersley L, Pryse S E, Walker I K, Heaton J A T, Mitchell C N, Williams M J and Willson C A (1996) ‘   Imaging of
                                                   ,
electron density troughs by tomographic techniques’ Proc. Ionospheric Effects Symposium 1996 (Ed.: J. Goodman),
Alexandria, VA, 11-18.




                                                        31
Kersley L, Pryse S E, Walker I K, Heaton J A T, Mitchell C N, Williams M J and Willson C A (1997) ‘Imaging of
                                                   ,
electron density troughs by tomographic techniques’ Radio Science 32, 1607-1621.

Kouris S S, Fotiadis D N, Xenos Th D and Jodogne J-C (1996) ‘ Ionospheric variability under quite and disturbed
           ,
conditions’ Doc 4067, Working Group Sessions of COST251, Prague, Czech Republic, 24-28 September 1996.

Kouris S S, Fotiadis D N and Xenos Th D (1997) ‘Some remarks on the day-to-day variation of foF2 and M(3000)F2,
Joint COST251/IRI Workshop, Kühlungsborn, Germany, 26-31 May, 1997.

Kuleshova V P, Karpachev A T, Pulinets S A and Shubin V I (1997) ‘                            ,
                                                                  Ionospheric storm modelling’ Joint
COST251/IRI Workshop, Kühlungsborn, Germany, 26-31 May, 1997.

Kumluca A, Tulunay E and Tulunay Y (1997) ‘    Forecasting of ionospheric critical frequency one hour advance using
                           ,
artificial neural networks’ Joint COST251/IRI Workshop, Kühlungsborn, Germany, 26-31 May, 1997.

Kutiev I, and Muhtarov P (1996) ‘Theoretical spatial and temporal ionospheric modelling: Storm conditions’ Working
Group Sessions of COST251, Prague, Czech Republic, 24-28 September 1996.

Kutiev I, Mukhtarov Pl and Bradley P A (1997) ‘Penetration of ionospheric disturbances in European sector studied by
                                    ,
an instantaneous mapping technique’ Joint COST 251/IRI Workshop and Working Group Sessions Proceedings, (Ed:
A Vernon) Kühlungsborn, Germany, COST251TD(97)006 (Part I), 51-58.

                                   On                                                   ,
Lamming X. and Lj R Cander (1997) ‘ improving ionospheric prediction by neural networks’ Presentation at the
Joint COST 251/IRI Workshop, Kühlungsborn, Germany, 27-30 May 1997.

Lastovicka J (1996a) ‘Long-term trends in the upper middle atmosphere as detected by ionospheric measurements’,
XXXI Assembly COSPAR, Birmingham, July 1996, Advances in Space Research, to be published.

Lastovicka J (1996b) ‘Similarities in the variability of the lower ionosphere and foF2 in the period range of 2-15
     ,
days’ Advances in Space Research, 18, 3, 117-120.

Lastovicka J (1996c) ‘                                                                                         ,
                      Effects of geomagnetic storms in the lower ionosphere, middle atmosphere and troposphere’ J
Atmos Terr Phys., 58, 831-843.

Lastovicka J and Mlch P (1996) ‘Solar cycle effect on oscillations in the period range of 2-20 days in the F-region of
               ,
the ionosphere’ Ann Geofisica, 39, 783-790.

Lastovicka J (1997) ‘  Oscillations of the planetary wave-type in the F region parameters over Europe compared to
                                     ,
oscillations in the lower ionosphere’ Joint COST251/IRI Workshop, Kühlungsborn, Germany, 26-31 May, 1997.

Leitinger R (1996) ‘            ,
                    Tomography’ Modern Ionospheric Science (eds.: H. Kohl, R. Ruester, K. Schlegel), ProduServ
GmbH Verlagsservice, Berlin, 1996, 346 - 370.

Leitinger R and Kirchengast G (1996) ‘                                                          ,
                                      Assessment of ionosphere tomography and imaging potential’ (= Section 4 of
Final Report ESTEC/11024/94/NL/CN), 16 pp.

Leitinger R, Ciraolo L, Jakowski N, Jodogne J-C, Kersley L and Spalla P (1996a) ‘ The future of TEC data collection
                                                          ,
and their use for mapping, modelling and now casting’ Proceedings of the First Workshop of COST 251 (Ed: J
Laštovicka), Institute of Atmospheric Physics, Prague, Czech Republic., 1996, COST251TD(96)017, 32-51.

Leitinger R, Kirchengast G and Ladreiter P (1996b) ‘                                             ,
                                                     Ionosphere tomography with GPS/MET and NNSS’ Proc.
Ionospheric Effects Symposium 1996 (Ed: J Goodman), Alexandria, VA, 84-91.

Leitinger R, Ladreiter P and Kirchengast G (1997a) ‘ Ionosphärentomographie mit GNSS Okkultationsdaten und
                                   ,
ionosphärischen Elektroneninhalten’ Kleinheubacher Berichte 40, 208-217.

Leitinger R, Ladreiter P and Kirchengast G (1997b) ‘ Ionospheric tomography with data from satellite reception of
                                                                                                            ,
Global Navigation Satellite System signals and ground reception of Navy Navigation Satellite System signals’ Radio
Science 32, 1657-1669.



                                                         32
Levy M F and Bamford R A (1997) ‘       Validation of N(h) profile models by oblique incidence sounding data’,
Presentation at the Joint COST 251/IRI Workshop, Kühlungsborn, Germany 27-30 May 1997.

Lundborg B and Broms M (1996) ‘       The DAMSON ionospheric sunding equipment; capabilities and results’  ,
Proceedings of the First Workshop of COST 251 (Ed: J. Laštovicka), Prague, Czech Republic, COST251TD(96)017,
131-141.

Mikhailov A V and Mikhailov V V (1997) ‘  Monthly median foF2 and M(3000)F2 ionospheric model over extended
           ,
PRIME area’ Presentation at the Joint COST 251/IRI Workshop, Kühlungsborn, Germany, 27-30 May 1997.

Mitchell C N, Kersley L and Pryse S E (1997) ‘The effects of receiver location in two-station experimental ionospheric
            ,
tomography’ J Atmos Terr Phys 59, 1411-1415.

Muhtarov P and Kutiev I (1997) ‘                                                          ,
                                Empirical modelling of ionospheric storms at midlatitudes’ Joint COST251/IRI
Workshop, Kühlungsborn, Germany, 26-31 May, 1997.

                                         A
Pancheva D and Mukhtarov P (1996) ‘ single station spectral model of the monthly median F-region critical
          ,
frequency’ Annali Geofisica, 39, 4, 807-818.

                                                                     A
Papandoniou V Ph, Fotiadis D N, Kouris S S and Xenos Th D (1997) ‘ study on the response of foF2 to different
                          ,
indices of solar activity’ Presentation at the Joint COST 251/IRI Workshop, Kühlungsborn, Germany, 27-30 May
1997.

Pryse, S E, Kersley L and Walker I K (1996) ‘                                                   ,
                                             Blobs and irregularities in the auroral ionosphere’ J Atmos Terr Phys,
58, 205-215.

Pulinets S A (1997) ‘                                                              ,
                     New visualization technique for ionospheric variability study’ Poster presentation at Joint
COST251/IRI Workshop, Kühlungsborn, Germany, 26-31 May, 1997.

Rothkaeh H F, Šmilauer J and Förster M (1997) ‘Dynamic changes in the outer ionosphere in the region of the ionospheric
                                        ,
trough during an intense magnetic storm’ Advances in Space Research, to be published.

Rothleitner W, Leitinger R and Kirchengast G (1996) ‘        Review on ionospheric tomography and associated
                          ,
reconstruction techniques’ (= Section 2.5 of Final Report ESTEC/11024/94/NL/CN), 13 pp.

Sardon E, Jakowski N and Schlueter S (1997) ‘Comparisons between IRI TEC predictions and the TEC obtained from
         ,
GPS data’ Presentation at the Joint COST 251/IRI Workshop, Kühlungsborn, Germany, 26-31 May, 1997.

                                             On
Scotto C, Radicella S M and Zolesi B (1997) ‘ the prediction of F1 ledge occurrence and critical frequency’,
Advances in Space Research, to be published.

Singer W (1997) ‘   Comparison of empirical D-region electron density models with radio wave propagation data’,
Presentation at the Joint COST 251/IRI Workshop, Kühlungsborn, Germany, 27-30 May 1997.

SolŠ J G (1997) ‘    Relation between hourly monthly median values of foF2 and some geophysical indices; its
                                                   ,
application to an ionospheric single station model’ Acta Geophys Polonica, to be published.

Sole J G and Altadill D (1997) ‘                                         ,
                                Ionospheric variability at fixed heights’ Working Group Sessions of COST251,
Kühlungsborn, Germany, 26-31 May, 1997.

Stanislawska I (1996) ‘                                             ,
                       Ionospheric Despatch Centre in Europe (IDCE)’ Working Group Sessions of COST251,
Prague, Czech Republic, 24-28 September 1996.

                                           A
Stanislawska I and Juchnikowski G (1996): ‘ single station prediction model as a source of additional screen-points
                  ,
for PRIME model’ Annali Geofisica, 39, 4, 839-843.

                                          A                                                             ,
Stanislawska I and Juchnikowski G (1997) ‘ note on use of screen points in regional ionospheric mapping’ Acta Geophys
Polonica, to be published.




                                                          33
Stanislawska I, Gulyaeva T, Juchnikowski G, Milodrowska M, Alberca L F, Bradley P A, Bremer J, Cannon P,
Hanbaba R, Jodogne J-C, de la Morena B, Radicella S M, and Tulunay Y (1997) ‘   European ionospheric despatch
              .
Centre- IDCE’ Presentation at the Joint COST 251/IRI Workshop, Kühlungsborn, Germany 27-30 May 1997.

Tulunay Y (1996) ‘  Interplanetary Magnetic Field (IMF) and its possible effects on the mid-latitude ionosphere III’,
Annali di Geofisica, 39, 4, 853-862.

Tulunay Y, Kaya A and Öke G (1997) ‘        The further possible effect of the IMF turnings on the Slough critical
                                                                                   ,
frequencies and the signature of the electron density trough on the COST251 area’ Joint COST251/IRI Workshop,
Kühlungsborn, Germany, 26-31 May, 1997.

Van der Perre L and Van de Capelle (1996) ‘                                                   ,
                                            Past, present and future of HF channel simulators’ Proceedings of the
First Workshop of COST 251 (Ed: J. Laštovicka), Prague, Czech Republic, COST251TD(96)017, 124-130.

Vasilievic I M and Cander Lj R (1997) ‘                                                           ,
                                       Forecasting of ionospheric storms: a case at mid-latitudes’ Joint COST
251/IRI Workshop and Working Group Sessions Proceedings, (Ed: A Vernon) Kühlungsborn, Germany,
COST251TD(97)006 (Part I), 98-108.

Walker I K, Heaton J A T, Kersley L, Mitchell C N, Pryse S E, and Williams M J (1996) ‘EISCAT verification in the
                                      ,
development of ionospheric tomography’ Ann Geophys 14, 1413-1421.

Warnant R (1996): ‘Etude du comportemant du Contenu Electronic Total et de ses irregularites dans une region de
                                                                            ,
latitude moyenne. Application aux calculs de positions relatives par le GPS’ PhD thesis Lovain-la-Neuve, June 17
1996.

Xenos Th D, Kouris S S and Papandoniou V Ph (1996) ‘                      ,
                                                    Single-station models’ Proceedings of the first COST 251
Workshop, COST251TD(96)017, Prague, Czech Republic, 15-31.

Xenos Th D, Kouris S S, Papandoniou V Ph and Fotiadis D (1997) ‘  Comparisons between different single station
       ,
models’ Presentation at the COST 251/IRI Workshop, Kühlungsborn, Germany 27-30 May 1997.

                                                  A                                              ,
Zolesi B, Cander Lj R and De Franceschi G (1197) ‘ regional model for the extended European area’ Presentation at
the Working Group Sessions of COST251, Kühlungsborn, Germany, 26-31 May 1997.




9.      Other presentations at meetings

Alberca L F, Juchnikowski G, Kouris S S, Mir• G, de la Morena B, Pancheva D, Mukhtarov Pl, SolŠ G, Stanislawska
I, Villanueva L and Xenos Th D (1997) ‘                                                            ,
                                         Comparison of different single station ionospheric models’ COST 251/IRI
Workshop, Kühlungsborn, Germany, 26-31 May 1997.

Alberca L F, Juchnikowski G, Mir• G, de la Morena B, Pancheva D, Mukhtarov Pl, SolŠ G, Stanislawska I and
Villanueva L (1997) ‘                                                            ,
                     Comparison of different ionospheric models in European area’ COST 251/IRI Workshop,
Kühlungsborn, Germany, 26-31 May 1997.

Altadill D, Apostolov E M and Hanbaba R (1997) ‘   Contributions of quasi periodic oscillations (2-35 days) to the
                    ,
variability of foF2’ Working Group Sessions of COST251, Kühlungsborn, Germany, 26-31 May, 1997.

Boska J (1996) ‘                                        ,
                Gravity wave activity in the ionosphere’ Paper G7.3, XXV Assembly URSI, Lille, September 1996.

Boska J and Knizova P (1997) ‘                                                         ,
                              Response of the ionosphere to strong tropospheric events’ XXII Assembly EGS,
Wien, April 1997.

Bremer J (1997) ‘                                                       ,
                  Post storm effects in middle and subauroral latitudes’ Joint COST251/IRI Workshop,
Kühlungsborn, Germany, 26-31 May, 1997.




                                                         34
Buresova D, Mosert de Gonzalez M, and Adeniyi J O (1996) ‘      Positive and negative storm effects on the electron
                                      ,
density profile at low solar activity’ Paper C4.2-0051, XXXI Assembly COSPAR, Birmingham, July 1996, Advances
in Space Research, to be published.

Gulyaeva T L (1996) ‘                                                       ,
                     Proposed menu for the ionosphere storminess assessment’ Paper C4.2-0041, XXXI Assembly
COSPAR, Birmingham, July 1996.

Gulyaeva T L (1996) ‘                                                      ,
                     Catalogue of midlatitude geomagnetic storms 1976-1995’ Doc 4015, Working Group Sessions
of COST251, Prague, Czech Republic, 24-28 September 1996.

Kishcha P V and Reck R (1996) ‘       Scenario of short term ionospheric forecasting at mid-latitudes’,
COST251TD(96)017, First Workshop of COST251, Prague, Czech Republic, 27 September 1996, 113-123.

Lastovicka J (1996) ‘                                                                              ,
                     Observations of tides and planetary waves in the atmosphere-ionosphere system’ invited paper
C1.1-0066, XXXI Assembly COSPAR, Birmingham, July 1996, Advances in Space Research, to be published.

Lastovicka J, Apostolov E and Altadill D (1996) ‘Vertical coupling via planetary waves?’ Paper C1.1-0071, XXXI
Assembly COSPAR, Birmingham, July 1996.

Lastovicka J and Knizova P (1997) ‘                                                                      ,
                                     Planetary wave-type oscillations in F-region parameters over Europe’ XXII
Assembly EGS, Wien, April 1997.
Radicella S M (1996) ‘                             ,
                       Variability and forecasting’ WG5, Working Group Sessions of COST251, Prague, Czech
Republic, 24-28 September 1996.

Radicella S M and De Franceschi G (1996) ‘Forecast and ionospheric variability with particular reference to high
         ,
latitude’ COST251TD(96)017, First Workshop of COST251, Prague, Czech Republic, 27 September 1996, 69-75.

 Rek R and Tsedilina E E (1996) ‘Relation between magnetic and ionospheric storms at midlatitude during 1993-
     ,
1995’ Working Group Sessions of COST251, Prague, Czech Republic, 24-28 September 1996.

                                      A
Warnat R and Jodogne J-C (1997) ‘ comparison between the TEC computed using GPS and ionosonde
             ,
measurements’ International Beacon Satellite Symposium, Sopron, Hungary, June 30- July 5, 1997.




                                                        35
                                                                    Annex I

Name for Work Package participation
A Akram                         DRA, Space and Communications Dept, Malvern, Worcs. UK
L F Alberca                     Observatori de l'Ebre, Roquetes, Spain
D Altadill                      Observatori de l'Ebre, Roquetes, Spain
O Altinay                       Barkod Bilgisayarli Kontrol Sistemleri, Ankara, Turkey
E Apostolov                     Academy G. Bonchev, Sofia, Bulgaria
F Arikan                        Hacettepe University, Ankara, Turkey
R A Bamford                     Rutherford Appleton Laboratory, Chilton, Didcot, UK
L W Barclay                     Lancaster University, c/o Barclay Associates, Chelmsford, UK
C Bianchi                       Istituto Nazionale di Geofisica, Rome, Italy
J Boska                         Geophysical Institute, Prague, Czech Republic
A Bourdillon                    University of Rennes 1, Rennes, France
A H Bilge                       MRC TUBITAK, Gebze, Turkey
P A Bradley                     Private Expert, Slough, UK
J Bremer                        Observatory for Atmospheric Research, Kühlungsborn, Germany
M Bröms                         Defence Research Establishment, Linköping, Sweden
D Buresova                      Geophysical Institute, Prague, Czech Republic
Lj R Cander                     Rutherford Appleton Laboratory, Chilton, Didcot, UK
P Cannon                        DRA, Space and Communications Dept, Malvern, Worcs. UK
G Ciraolo                       IROE, Florence, Italy
P Clark                         University of Leeds, Leeds, UK
Th Damboldt                     Private Expert, Darmstadt, Germany
M Darnell                       University of Leeds, Leeds, UK
M I Dick                        Rutherford Appleton Laboratory, Chilton, Didcot, UK
O Ekblom                        Ministry for Foreign Affairs, Stockholm, Sweden
A Eliseyev                      University of St Petersburg, St Petersburg, Russia
C B Erol                        Baskent University, Ankara
E Feichter                      Karl-Franzens-Universitat, Graz, Austria
G Fontana                       Istituto Nazionale di Geofisica, Rome, Italy
D Fotiadis                      Aristotelian University of Thessaloniki, Thessaloniki, Greece
G de Franceschi                 Istituto Nazionale di Geofisica, Rome, Italy
V Gherm                         Institute of Radiophysics, University of St Petersburg, St Petersburg, Russia
G I Gordienko                   Institute of Ionosphere, Academy of Sciences, Almaty, Kazakstan
G Gott                          UMIST, Manchester, UK
C Goutelard                     University of Paris 11, Orsay, France
T L Gulyaeva                    IZMIRAN, Moscow, Russia
R Hanbaba                       France Telecom CNET, Lannion, France
M Herraiz                       Universidad Complutense, Madrid, Spain
G P Hochegger                   Karl-Franzens-Universitat, Graz, Austria
N Jakowski                      DLR, Neustrelitz Observatory, Neustrelitz, Germany
J-C Jodogne                     Institut Royal Meteorologique de Belgique, Brussels, Belgium
G Juchnikowski                  Space Research Centre, Warsaw, Poland
A T Karpachev                   IZMIRAN, Moscow, Russia
L Kersley                       University of Wales, Penglais, Aberystwyth, Dyfed, UK
G Kirchengast                   Karl-Franzens-Universitat, Graz, Austria
P V Kishcha                     IZMIRAN, Moscow, Russia
P Knizova                       Geophysical Institute, Prague, Czech Republic
S Kouris                        Aristotelian University of Thessaloniki, Thessaloniki, Greece
I Kutiev                        Academy G Bonchev, Sofia, Bulgaria
X Lamming                       France Telecom CNET, Lannion, France
P Lassudrie Duchesne France Telecom CNET, Lannion, France
J Lastovicka                    Geophysical Institute, Prague, Czech Republic
R Leitinger                     Karl-Franzens-Universitat, Graz, Austria
Y Le Roux            France Telecom CNET, Lannion, France
T Lesyer                        Swedish Institute of Space Physics, Uppsala, Sweden
M Levy                          Rutherford Appleton Laboratory, Chilton, Didcot, UK
M Lissimore                     DRA, Space and Communications Dept, Malvern, Worcs. UK
B Lundborg                      Defence Research Establishment, Linköping, Sweden
A Mikhailov                     Institute for Applied Geophysics of Russia, Moscow, Russia
G Miro                          Centro de El Arenosillo, Mazagon, Spain
P Mlch                          Geophysical Institute, Prague, Czech Republic
M Moorhead                      Neptune Radar, Gloucester, UK
P Muhtarov                      Academy G Bonchev, Sofia, Bulgaria
B A De la Morena                Centro de El Arenosillo, Mazagon, Spain
J Nilsson                       Defence Research Establishment, Linköping, Sweden
D Pancheva                      Academy G Bonchev, Sofia, Bulgaria
S Pau                           Istituto Nazionale di Geofisica, Rome, Italy
L Perrone                       Istituto Nazionale di Geofisica, Rome, Italy
P Pesec                         Karl-Franzens-Universitat, Graz, Austria
J Pijoan Vidal                                                          La         ,
                                Escuela de Telecomunicaciones ‘ Salle’ Barcelona, Spain
E Pryse                         University of Wales, Penglais, Aberystwyth, Dyfed, UK
S A Pulinets                    IZMIRAN, Moscow, Russia
S Radicella                     International Centre for Theoretical Physics, Trieste, Italy
H Rothkaihl                     Space Research Centre, Warsaw, Poland
A Sancisi                       University of Wales, Penglais, Aberystwyth, Dyfed, UK


                                                                           36
C Scotto          Istituto Nazionale di Geofisica, Rome, Italy
J Serrat          Escuela Tecnica Superior de Ingenieros de Telecomunicaciones, Madrid, Spain
V Shubin          IZMIRAN, Moscow, Russia
W Singer          Observ. for Atmospheric Research, Kühlungsborn, Germany
G Sole            Observatori de l'Ebre, Roquetes, Spain
P Spalla          IROE, Florence, Italy
I Stanislawska    Space Research Centre, Warsaw, Poland
H Strangeways     University of Leeds, Leeds, UK
P Sudworth        JPS Associates (UK) Ltd, Farnborough, Hants, UK
E Tulunay         The Middle East Technical University, Ankara, Turkey
Y Tulunay         The Middle East Technical University, Ankara, Turkey
E Turunen         Geophysical Observatory, Sodankyla, Finland
L Van der Perre   Katholic University of Leuven
L Villanueva      Universidad Complutense, Madrid, Spain
I Vasiljevic      Geomagnetic Institute, Grocka, Belgrade, Serbia
A Vernon          Rutherford Appleton Laboratory, Chilton, Didcot, UK
J M Vilaplana     Centro de El Arenosillo, Mazagon, Spain
T Xenos           Aristotelian University of Thessaloniki, Thessaloniki, Greece
E Yazgan          Hacettepe University, Ankara, Turkey
K Yudakhin        IZMIRAN, Moscow, Russia
N Zernov          Institute of Radiophysics, University of St Petersburg, St Petersburg, Russia
M-L Zhang         International Centre for Theoretical Physics, Trieste, Italy
B Zolesi          Istituto Nazionale di Geofisica, Rome, Italy




                                                            37
                                                 Annex II
  List of temporary documents circulated, presented at MC meetings and Workshops in the period under review

COST251TD(96)015         D Pancheva and P       A single-station spectral model of the monthly median E-region
                            Mukhtarov           critical frequency.
COST251TD(96)016       O Altynay, E Tulunay     Prediction of ionospheric critical frequency using neural networks.
                          and Y Tulunay
COST251TD(96)017       J Lastovicka (contact)   Proceedings of the 1st Workshop of COST 251 held in Prague, Czech
                                                Republic, September 1996.
COST251TD(96)018       Lj R Cander and P A      Electron-density height profile model testing.
                              Bradley
COST251TD(96)019       X Lamming and Lj R       Appropriateness of the neural network approach for monthly median
                              Cander            ionospheric prediction.
COST251TD(96)020     M F Levy, M I Dick and     RAL databank of VI soundings.
                           Lj R Cander
COST251TD(96)021       P A Bradley and Lj R     The COST 251 ionospheric map and model program (IMMP).
                              Cander
COST251TD(96)022     I Kutiev and P Muhtarov  Theoretical spatial and temporal ionospheric modelling: Storm
                                              conditions.
COST251TD(96)023         S A Pulinets, V K    Total height profiles of electron density over European part of FSU
                     Depuev, A T Karpachev by vertical sounding data (ground based, Intercosmos 19 and Comos
                        and N A Kochenova 1809).
COST251TD(96)024           I Stanislawska     Deviations from the monthly median.
COST251TD(96)025              J Bremer        Some additional results of long-term trends in vertical-incidence
                                              ionosonde data.
COST251TD(96)026            J Lastovicka      Long-term trends in other ionospheric characteristics.
 OST251TD(96)027         M I Dick and Lj R    Multiquasi-parabolic model ionospheres for determination of HF ray-
                               Cander         paths.
COST251TD(96)028          L F Alberca, G      Single-station prediction models foe remote area in instantaneous
                      Juchnikowski, J G Sole mapping.
                        and I Stanislawska,
COST251TD(96)029     L F Alberca, D Altadill, Ionospheric single station models.
                        M De la Morena, M
                     Herraiz, G Juchnikowski,
                         G Miro, J G Sole, I
                         Stanislawska, J M
                          Vilaplana and L
                             Villanueva
COST251TD(96)030     L Villanueva, M Herraiz, Vertical electron density profile N(h) model comparisons for El
                     B De la Morena, G Miro, Arenosillo.
                        J M Vilaplana, B E
                      Reinisch and X Huang
COST251TD(96)031       Y Tulunay, A H Bilge The theoretical spatial and temporal modelling - Quite conditions.
                          and S A Baykal
COST251TD(96)032       A T Karpachev, M G Statistical characteristics of different ionospheric troughs on
                           Deminov, S K       longitude, local time, season, storm phase and geomagnetic indices.
                     Annakuliev, V V Afonin, A review.
                             Y Smilauer
COST251TD(96)033     A T Karpachev and S A Model presentation of F2 layer characteristics (Ne, Te, NmF2, hmF2)
                               Pulinets       vicinity of main trough.
COST251TD(96)034              A Vernon        Minutes of the Fourth Management Committee meeting of COST
                                              251 Improved quality of Ionospheric Telecommunication System
                                              planning and operation (IITS), Institute of Atmospheric Physics,
                                              Academy of Sciences of Czech Republic, Prague, Czech Republic,
                                              24-28 September 1996.



                                                       38
    Reference             Author                                            Title
COST251TD(97)001 J Lastovicka, M F Levy, Specification of COST 251 databank, January 1997.
                 S Radicella and P Spalla
COST251TD(97)002   N S Wheadon and I D An HF ionospheric channel simulator implementation on a multi-
                           Alston          processor DSP card (prepared for COST 251 WG 4(UK)), January
                                           1997.
COST251TD(97)003 J Lastovicka, M F Levy, Various reports from COST 251 Short-term scientific missions,
                      M Moorhead, A        February 1997.
                 Bourdillon, E Tulunay, J
                      M Viliplana, B
                   Lundborg, L Van der
                   Perre, Lj R Cander, F
                          Arikan
COST251TD(97)004       T Gulyaeva, I       Current status and prospects of daily exchange of the ionospheric
                     Stanislawska, L F     data and forecasts via IDCE, April 1997.
                   Alberca, J Bremer, M
                    Broms, P Cannon, R
                 Hanbaba, J-C Jodogne, G
                     Juchnikowski, Th
                   Leyser, M F Levy, M
                   Milodrowska, B de la
                  Morena, S M Radicella
                      and Y Tulunay
COST251TD(97)005     Pl Muhtarov and I     A method of filling up the gaps in monthly tables of ionospheric
                           Kutiev          characteristics, May 1997.
COST251TD(97)006       Ed: A Vernon        Proceedings of joint COST 251/IRI Workshop and Working Group
     (Part I)                              Sessions, Kühlungsborn, Germany, 27-30 May 1997. September
                                           1997.
COST251TD(97)006      Ed: B Lundborg       Proceedings of joint COST 251/IRI Workshop and Working Group
     (Part II)                             Sessions, Kühlungsborn, Germany, 27-30 May 1997. September
                                           1997.
COST251TD(97)007         A Vernon          Minutes of the Fourth Management Committee meeting of COST
                                           251 Improved quality of Ionospheric Telecommunication System
                                           planning and operation (IITS), Institute of Physics, Kühlungsborn,
                                           Germany, 26-31 May 1997. September 1997.
COST251TD(97)008 M I Dick and I Vasiljevic The COST 251 VI ionospheric digital database. September 1997.

COST251TD(97)009             A Vernon         Minutes of WG Leader meeting, Rome, 11-13 September 1997.
    (Rev 1)                                   October 1997.
COST251TD(97)010            R Hanbaba         COST 251 Second Annual Report (Period July 1996 - June 1997).
                                              October 1997.




                                                     39

								
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