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					The ionospheric scale heights
derived from the incoherent
scatter radar measurements

         Libo LIU
         Institute of Geology and Geophysics
         Chinese Academy of Sciences
         Beijing, CHINA

         Email: liul@mail.iggcas.ac.cn
Outline
•Ionospheric scale heights
    Expressions of altitude profile of Ne
    Definitions of ionospheric scale heights

•Incoherent Scatter Radar (ISR) data set

•Result & Summary
Functions of electron density
profiles in the ionosphere

Many mathematical functions:
  Chapman function, exponential,
  parabolic, Epstein functions, and …
are used to describe the altitude profile of Ne.
The scale height is evidently a key parameter
in these functions to determine the shape of
ionospheric Ne profiles.
Related studies on
ionospheric scale heights
(1) Bottomside
    Scale heights are relatively easy to be
    deduced from ground-based ionosonde
    and other measurements [e.g., Huang and Reinisch,
    2001; Reinisch and Huang, 2004].

(2) Topside
   Scale heights are derived from incoherent
   scatter radars, topside sounders [e.g., Belehaki et
   al., 2006; Kutiev et al., 2006], and radio occultation
   measurements [e.g., Stankov and Jakowski, 2006].
Ionospheric scale heights
•Plasma scale height (Hp)
        Hp=kb(Ti+Te)/mig

•Vertical scale height (VSH)



•Effective scale height (Hm)



Strictly speaking, VSH and Hm are virtually the distribution
heights of electron density profiles.
Fit with Chapman-α profile function                O:   observed



   exponential fit

                                      linear fit        linear fit

      log10(Ne) (m-3)


Figure. An example of ISR altitude profiles of Ne, Ti
        and Te within half an hour.
Data Base
Arecibo ISR data (1966-2002), which are archived in
the NCAR CEDAR database, are analyzed without
specifying the measurement modes.
These data have a typical altitude resolution of about
23 km prior to 1985 and 37 km in subsequent years.
Median ISR Ne, Te, and Ti profiles are determined
within every 30 minute interval in each day.

Thus more than 16,000 mean profiles are derived
from more than 90,000 raw Ne profiles in the Arecibo
ISR database.
P=(F107+F107A)/2




                   8
Arecibo   Local Noon




                       9
Arecibo   Local Midnight




                           10
Geomagnetic activity effects
      Millstone Hill ISR, October 21 to November 5, 2002.
Geomagnetic activity dependences of
Hm over Wuhan (midday)




                          [Liu et al., Annales
                          Geophysicae, 2006]
Relationship between VSH and Hp

                    Arecibo
                                          Hp=kb(Ti+Te)/mig




 Figure. Diurnal variation of the ratios of VSH to Hp, VSH/Hp.
Relationship between VSH and Hp



                   Diffusion effect Thermal gradient
                                [Liu et al., JGR, 2007]



                                             Nighttime




                       Daytime
Relationship between VSH and Hm
Diurnal variation of the ratios of
VSH to Hm, VSH/Hm.
                    Arecibo
                                     The ratio of VSH to Hm
                                     changes from 3.2 at daytime
                                     to 2.7 at night.
Summary
•This investiagtion shows that the topside ionospheric
scale heights VSH, Hp and Hm have appreciable diurnal
and seasonal variations.
•VSH, Hm, and Hp tend to increase with increasing
solar flux.
•Both the contributions from the topside thermal
structure and diffusion processes can greatly influence
the ratio of VSH to Hp.
   Thanks for your attention!



Liu L., et al. (2007), An analysis of the scale heights in the
lower topside ionosphere based on the Arecibo incoherent
scatter radar measurements, J. Geophys. Res., 112,
doi:10.1029/2007JA012250.

				
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posted:6/25/2011
language:English
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