Fall Meeting SA MC Hall Friday Presiding by benbenzhou

VIEWS: 4 PAGES: 3

									                                                                                                                                       2000 Fall Meeting               F929
provided by atmospheric gravity waves (AGWs) propa-          SA51A-10 1130h                                               David J. Sahnow1
gating zonally and dissipating, and through coriolis in-
fluences evolves the meridional flow for the respective                                                                   Jeffrey W. Kruk1
                                                             Imaging Space Weather Impacts in the
hemisphere. Presumably, the AGWs of tropospheric
origin drive (provides the fuel for) the meridional circu-     Thermosphere                                               Edward M. Murphy1
lation which results in upwelling in the (cold) summer
pole, and downwelling in the winter. The well known           Larry J Paxton1 (240 228 6871;                              H. Warren Moos1
upwelling in the summer transports upper tropospheric                                                                     1 Johns Hopkins University, Department of Physics
water vapor to the mesosphere producing a cold (and             larry.paxton@jhuapl.edu); Daniel Morrison1 (240
                                                                228 4172; daniel.morrison@jhuapl.edu); Douglas J             and Astronomy, Baltimore, MD 21218, United
cloudy) mesosphere. Little attention has been given to
                                                                                                                             States
the winter pole downwelling, which transports solar in-         Strickland2 (703 204 1302; dstrick@cpi.com);
                                                                                                                             During orbital verification, the Far Ultraviolet
fluenced lower thermosphere constituents to the lower           Andrew B. Christensen3 (310 336 7084;
atmosphere. This big picture cell will be discussed as                                                                   Spectroscopic Explorer (FUSE) obtained spectra of the
                                                                andrew.b.christensen@aero.org); Ching-I ‘ Meng1          terrestrial day airglow between 905 and 1184 ˚ from an
                                                                                                                                                                      A
well as number of considerations which should be inves-
                                                                (240 228 5409; ching.meng@jhuapl.edu); Geoff             altitude of 766 km. The spectrographs have three aper-
tigated to mature the understanding of this coupling
process including the mechanisms which drive the cell           Crowley4; Matthew McHarg5                                tures that can simultaneously record the atmospheric


                                                                                                                                                                                     S
                                                                                                                         emissions with limiting instrumental spectral resolu-
and the constituents which downwell to influence the          1 The Johns Hopkins University Applied Physics Lab-
lower atmosphere.                                                                                                        tions of approximately 0.4, 0.05, and 0.03 ˚. Seven or-
                                                                                                                                                                    A
                                                                 oratory, 11100 Johns Hopkins Rd., Laurel, MD            bits were obtained of observations of the sunlit Earth
                                                                 20723, United States
                                                              2 Computational Physics, Inc., 2750 Prosperity Ave
                                                                 Ste 600, Fairfax, VA 22031, United States
                                                                                                                         and disclose a wealth of emissions resulting from the
                                                                                                                         electron impact excitation of N2 in addition to emis-
                                                                                                                         sions of O, N, and N+ produced by both photoelectron
                                                                                                                                                                                     A
                                                                                                                         impact and by photodestructive excitation and ioniza-
                                                              3 The Aerospace Corporation, POB 92957 MS254, Los
SA51A-08 1055h                                                   Angeles, CA 90009, United States
                                                                                                                         tion of thermospheric O and N2 by extreme ultraviolet
                                                                                                                         solar radiation. The argon resonance transitions are
                                                              4 Southwest Research Institute, 6220 Culebra Rd, San       unambiguously identified as are previously unreported
                                                                                                                         transitions between highly excited energy levels of O+ .
                                                                 Antonio, TX 78238-5166, United States
Investigations of Auroral Thermospheric                                                                                  These spectra have the highest spectral resolution and
                                                              5 HQ USAFA/DFP , 2354 Fairchild Drive Suite 2A31,          sensitivity in this spectral range to date and will pro-
  Heating Mechanisms: the                                                                                                vide valuable input to the interpretation of lower res-
                                                                 USAF Academy, CO 80840, United States
  Joule/Lorentz Question Revisited.                                                                                      olution spectra from current and future Earth remote
                                                                 Space weather has observable consequences for ther-     sensing missions.
                                                             mospheric and ionospheric composition. A new gen-
 Richard L Balthazor 1 (+44 114 222 3711;                    eration of far ultraviolet (the FUV covers the wave-
   r.balthazor@sheffield.ac.uk)                              length range 110 to 180 nm) sensors will soon be pro-
                                                             ducing data in addition to the sensors on IMAGE and         SA52A-02 1330h POSTER
 Robert Erdelyi1 (+44 114 222 3832;                          POLAR. These sensors, GUVI on the TIMED satellite
   robertus@sheffield.ac.uk)                                 and SSUSI on DMSP, produce spectral images from low         Observation of Atomic Neon Emission
 Phil Williams2 (+44 1970 622817; pjw@aber.ac.uk)            Earth orbit.
                                                                                                                          Lines in Sky Spectra Obtained with
                                                                 We summarize the FUV signatures of auroral inputs
 1 Space and Atmosphere Research Group , University
                                                             and the response of the high latitude thermosphere to        the Keck/HIRES System on Mauna
    of Sheffield, Sheffield S3 7RH, United Kingdom           these inputs. Remote sensing has the fundamental limi-       Kea; Light Pollution or Nightglow?
                                                             tation that it is a column integrated measurement: this
 2 EISCAT Group, Department of Physics, University           limitation can be addressed in a number of ways which
                                                                                                                          Tom G Slanger 1 (650-859-2764;
    of Wales, Aberystwyth SY23 3BZ, United Kingdom           will be discussed. In this talk, FUV radiances com-
                                                             puted from TGCM simulations for quiet and disturbed            tom.slanger@sri.com)
                                                             conditions will be presented. These calculations show
    Thermospheric heating in the auroral regions is the                                                                   Philip C Cosby1 (650-859-6128;
                                                             that changes in thermospheric composition (described
production mechanism of Large-Scale Travelling At-                                                                          philip.cosby@sri.com)
                                                             as changes in the ratio of the O to N2 column den-
mospheric Disturbances (LS-TADs), otherwise known
as Atmospheric Gravity Waves (AGWs). The classi-
                                                             sity) can be tracked under sunlit conditions and in the      David L Huestis1 (650-859-3464;
                                                             region of auroral precipitation. Energetic particle pre-       david.huestis@sri.com)
cal view is that electric fields in the auroral regions
                                                             cipitation in the aurora leads to E-region ionization and
heat the thermosphere by a combination of Joule Heat-
                                                             enhancement of the Hall and Pedersen conductivity.           Donald E Osterbrock2 (803-459-2605;
ing (macroscopic frictional heating), Lorentz Forcing                                                                        don@ucolick.org)
                                                             The utility of data from IMAGE, POLAR, and MSX
(microscopic momentum transfer through collisions be-
                                                             to this problem will be discussed and compared to that       1 SRI International, 333 Ravenswood Ave.,        Menlo
tween ions and neutrals) and particle precipitation. Of
                                                             of SSUSI and GUVI.                                              Park, CA 94025, United States
these, it has been shown that above about 110 km,
                                                                 Future missions such as those envisioned within the
Joule heating is the dominant energy transfer mech-                                                                       2 Lick Observatory, University of Califorania Obser-
                                                             Living With a Star program could readily encompass a
anism by up to an order of magnitude. However, mod-                                                                          vatories, UC Santa Cruz, Santa Cruz, CA 95064,
                                                             global FUV imaging system.
elling studies of the Travelling Atmospheric Distur-                                                                         United States
bances (TIDs, the ionospheric signatures of the passage
                                                                                                                             Light pollution from urban areas is a serious prob-
of TADs) observed by the WAGS campaign have consis-
                                                                                                                         lem for astronomers. The Keck telescopes on Mauna
tently underestimated the amplitude of the TID/TAD           SA51A-11 1145h INVITED                                      Kea are located in an exceptionally clean area with re-
system observed at mid-latitudes by up to an order of
                                                                                                                         spect to extraneous light. However, low level mercury
magnitude. This study aims to investigate the discrep-
ancy between modelling and observation by examining          Space Weather Effects on Low Altitude                        radiation has been detected (ref. 1), and we now report
                                                               Spacecraft and Environment                                on the presence of 35 neon lines in spectra taken in the
both the observations themselves, and additional po-
                                                                                                                         580-810 nm region by the HIRES echelle spectrometer
tential heating mechanisms such as shock heating and
                                                                                                                         on Keck 1. Curiously, they have similar intensities to
MHD resonance.                                                Lawrence J. Zanetti 1 (1-240-228-6897;                     the mercury lines (50-200 milliRayleighs), which is not
                                                                larry.zanetti@jhuapl.edu)                                at all characteristic of urban light pollution. For exam-
                                                              Brian J. Anderson1 (1-240-228-6347;                        ple, the intensity of the Ne(585.25 nm) and Hg(546.08
                                                                 brian.anderson@jhuapl.edu)                              nm) lines is about the same. At Lick Observatory, over-
                                                                                                                         looking the city of San Jose, the intensity ratio of the
                                                              1 The Johns Hopkins University Applied Physics Lab-        strongest Hg line to the strongest Ne line is typically
SA51A-09 1110h INVITED                                           oratory, 11100 Johns Hopkins Road, Laurel, MD           100 (ref. 2). We are investigating the source of the
                                                                 20723-6099, United States                               neon radiation, and are considering ionospheric excita-
                                                                Neutral and ionospheric inflation as well as energy      tion, urban light pollution, and stray light from neon
                                                             deposition and current systems from magnetic storm,         lamps internal or external to the dome.
Space Weather Impact of Storm-Time                                                                                           This study was supported by NSF Aeronomy and
                                                             substorm, and solar particles event conditions are dis-
  Perturbations in the Thermosphere                          cussed as they relate to technological systems including    NASA Planetary Astronomy.
                                                             LEO spacecraft, shuttle and high altitude flight person-        1 D. E. Osterbrock, R. T. Waters, T. A. Barlow, T.
                                                             nel and electric power distribution systems. Specific       G. Slanger, and P. C. Cosby, PASP 112, 733 (2000).
 Timothy J Fuller-Rowell (303-497-5764;                                                                                      2 D. E. Osterbrock and A. Martel, PASP 104, 76
                                                             space weather events are cited from March 1989 and
   tjfr@sec.noaa.gov)                                        July 2000 major storm periods. Future NASA and in-          (1992).
 Space Environment Center, 325 Broadway, Boulder,            teragency programs to understand, specify and counter
   CO 80305-3328, United States                              space weather impacts will be reviewed.
                                                                                                                         SA52A-03 1330h POSTER
    During a geomagnetic storm, both thermospheric
density and composition are disturbed. The neutral                                                                       A Model-Comparative Investigation of
density fluctuations have a direct impact on opera-
tional systems by perturbing positions of low-Earth-         SA52A MC: Hall D Friday 1330h                                 2-D Ionospheric Remote Sensing
orbit satellites and space debris. The problem of colli-                                                                   Through the Inversion of UV
sion avoidance is of particular concern for the manned       Airglow, Chemistry and Hot Atoms                              Radiative Recombination Emissions
Space Station. The magnitude of the storm-time den-
sity change is modest, compared with changes due to
                                                             Posters
                                                                                                                          Farzad Kamalabadi 1 ((217)333-4406;
EUV over the solar cycle, but the response is rapid, and
therefore difficult to follow or predict. These changes      Presiding: T G Slanger, SRI                                    farzadk@uiuc.edu); J. Huba2; K. Dymond3; R.
still represent a challenge for empirical, or physical,          International                                              McCoy4; S. Budzien3; S. Thonnard3
drag models. Thermospheric composition changes dur-
                                                                                                                          1 University of Illinois at Urbana-Champaign, 1308
ing storms have an indirect impact on operational sys-
tems. During a disturbance, large-scale and regional                                                                         West Main, Urbana, IL 61801, United States
heating at high latitudes drives upwelling, and mixing,      SA52A-01 1330h POSTER                                        2 Plasma Physics Division, Naval Research Labora-
of the neutral gas. The altered ratio of molecular to
                                                                                                                             tory, Washington, DC 20375, United States
atomic species affects ion recombination and can lead        High Resolution FUV Spectroscopy of
to both depletions and enhancements in plasma den-                                                                        3 Space Science Division , Naval Research Laboratory,
sity. Of particular concern to operational systems is          the Terrestrial Day Airglow with                              Washington, DC 20375, United States
the presence of steep gradients in the medium. The             FUSE                                                       4 Office of Naval Research, 800 N. Quincy St, Arling-
ionospheric changes impact communication due to dis-
ruption of radio wave propagation, and induce errors                                                                         ton, VA 22217, United States
                                                              Paul D. Feldman1 (1-410-516-7339;
in single-frequency navigation positioning due to phase                                                                     Prominent optically thin UV emissions such as
                                                                pdf@pha.jhu.edu)
delay in the satellite signals.                                                                                             ˚
                                                                                                                         911A and 1356˚ produced by radiative recombination
                                                                                                                                      A


                                                                This page may be freely copied.
F930           2000 Fall Meeting
of O+ provide the means to obtain 2-dimensional night-     SA52A-06 1330h POSTER                                         SA52A-08 1330h POSTER
time F-region electron densities tomographically from a
series of space-based spectroscopic measurements. We                                                                     Proton Aurora: A Comparative Study
investigate the viability of simultaneously reconstruct-   Daytime Electron Density Profiles                                of Kappa and Maxwellian Incident
ing altitude profiles and latitude gradients of iono-
spheric electron densitiy structures in low latitudes
                                                             Derived by Analysis of the Low                                Fluxes
by inverting oxygen recombination data from space-           Resolution Airglow and Aurora
borne spectrograph limb scanning measurements ob-            Spectrograph (LORAAS)Data from                               Dwight T. Decker1 (781-377-5194;
tained from the NRL HIRAAS experiment on-board the
ARGOS satellite. Through several comparative case
                                                             the Advanced Research and Global                               Dwight.Decker@hanscom.af.mil)
studies we explore the performance of such remote sens-      Observing Satellite (ARGOS)
                                                                                                                          Bamandas Basu1 (781-377-3048;
ing approach in the context of SAMI2, a low-latitude                                                                        Bamandas.Basu@hanscom.af.mil)
ionospheric model developed at NRL, which solves the
                                                            Kenneth F Dymond1 (202-767-2816;
ion continuity and momentum equations for seven ion                                                                       John R. Jasperse1 (781-377-3083;
species and treats their dynamic plasma and chemical          dymond@tip.nrl.navy.mil); Scott A Budzien1;                    John.Jasperse@hanscom.af.mil)
evolution.                                                    Stefan E Thonnard1; Andrew C Nicholas1; Robert              1 Air Force Research Laboratory, 29 Randolph Road,
                                                              P McCoy2; Ronald J Thomas3                                     Hanscom AFB, MA 01731, United States
                                                            1 E O Hulburt Center for Space Research, Code 7623               Studies of ion population in the central plasma sheet
                                                                                                                         (CPS) have found that at high energies (E > charac-
SA52A-04 1330h POSTER                                          Naval Research Laboratory, Washington, DC 20375-
                                                                                                                         teristic energy) there is a nonthermal power-law tail
                                                               5352, United States
                                                                                                                         which can be fitted using a kappa distribution. Similar
An Evaluation of Low-Latitude                               2 Office of Naval Research, Code 321SR 800 N. Quincy         studies at ionospheric altitudes, carried out by com-
                                                                                                                         bining data from various instruments, have shown that
 EUV/FUV Emission Enhancements                                 Street, Arlington, VA 22217-5660, United States           the proton distributions have high-energy tails even at
 During Geomagnetic Storms                                  3 Department of Electrical Engineering, New Mexico
                                                                                                                         ionospheric altitudes and are similar to those seen for
                                                                                                                         earthward streaming protons in the outer boundary of
                                                               Institute of Mining and Technology, Socorro, NM           the plasma sheet. More recently, the Particle Environ-
 Andrew W Stephan1 (617-353-5990;                              87801, United States                                      ment Monitor (PEM) on board the Upper Atmosphere
   astephan@bu.edu); Supriya Chakrabarti1                      The High Resolution Airglow and Aurora Spec-
                                                                                                                         Research Satellite (UARS) has observed ionospheric ion
   (617-353-5990; supc@bu.edu); Kenneth F                                                                                spectra with a high-energy power-law tail. Previous
                                                           troscopy (HIRAAS) experiment was launched from
                                                                                                                         theoretical calculations of proton-hydrogen atom au-
   Dymond2 (202-767-2816;                                  Vandenberg AFB, CA aboard the Advanced Research and
                                                                                                                         rora assumed Maxwellian distributions for the incident
   dymond@tip.nrl.navy.mil); Scott A Budzien2              Global Observation Satellite (ARGOS) on 23 February 1999
                                                                                                                         proton spectra. In this paper, we present the impacts
   (202-767-9372; sab@tip.nrl.navy.mil); Stefan E          at 2:29:55 AM Pacific Standard Time. The ARGOS
                                                                                                                         that high-energy power-law tails have on the calcula-
   Thonnard2 (202-767-5041;                                is in a sun synchronous, circular orbit at an altitude
                                                                                                                         tions of the ionospheric effects of precipitating protons
                                                           of 843 Km.      The HIRAAS experiment contains the
   thonnard@tip.nrl.navy.mil); Robert P McCoy3             Low Resolution Airglow and Aurora Spectrograph (LO-
                                                                                                                         and compare them with those for pure Maxwellians.
   (703-696-8699; mccoy@tip.nrl.navy.mil)                  RAAS). The LORAAS gathers limb scans over the 750-
 1 Boston University Center for Space Physics, 725         100 Km altitude range, covering the 800-1700 ˚ pass-
                                                                                                            A
                                                           band at 17 ˚ resolution.
                                                                        A                                                SA52A-09 1330h POSTER
    Commonwealth Ave., Boston, MA 02215, United
    States                                                     We report our measurements of the electron den-
                                                           sity derived by analysis of the O I 1356 ˚ emission and
                                                                                                     A                   Yields of O2 Electronic States in
 2 E O Hulburt Center for Space Research, Code             a nearby set of N2 Lyman-Birge-Hopfield bands. The              Oxygen Atom Recombination
    7623 Naval Research Laboratory , Washington, DC        O I 1356 ˚ emission is primarily produced by photo-
                                                                      A
    20375, United States                                   electron impact excitation of O; however, the LORAAS
                                                           has observed stronger than expected contributions to           David L. Huestis1 (650-859-3464;
 3 Office of Naval Research , Code 321SR 800 N. Quincy                                                                      david.huestis@sri.com)
                                                           the emission from radiative recombination of O+ and
    St., Arlington, VA 22217, United States                electrons and O+ - O− neutralization. By properly ac-          Richard A. Copeland1 (650-859-6534;
                                                           counting for the radiative recombination and neutral-            richard.copeland@sri.com)
    We will use OI emission lines and N2 LBH bands ob-
                                                           ization contributions, we have been able to determine
served in the extreme- and far-ultraviolet (EUV/FUV)
                                                           daytime electron density profiles, while simultaneously        Tom G. Slanger1 (650-859-2764;
as a measure of the low-latitude composition of the                                                                         tom.slanger@sri.com)
                                                           retrieving the O, O2 , and N2 densities. We present the
thermosphere during geomagnetic storms. From this,
we can compare low-latitude (< 30◦ ) composition
                                                           retrieved electron density profiles and compare them           1 Molecular Physics Laboratory,      SRI International,
                                                           with peak heights and peak densities measured during              333 Ravenswood Ave., Menlo Park, CA 94025,
changes versus excitation by Energetic Neutral Atoms
                                                           ionosonde overflights. Our retrievals are in good agree-          United States
(ENAs) in the production of increased EUV/FUV air-
                                                           ment with the ionosonde measurements.                             By unifying laboratory measurements with field ob-
glow observed during this activity. We have observed
a significant storm-time increase in both the dayside                                                                    servations of the nightglows of Earth and Venus we have
and nightside EUV/FUV emissions measured by the                                                                          assembled a self-consistent picture of the production
STP78-1 satellite on March 22, 1979 and the Low Res-                                                                     and relaxation of the electronic states of O2 following
olution Airglow and Aurora Spectrograph (LORAAS)                                                                         oxygen atom recombination.
on the Advanced Research and Global Observation            SA52A-07 1330h POSTER                                             In the past it has been assumed [1-2] that mixing
Satellite (ARGOS) on October 22, 1999. The nearly-                                                                       of O2 electronic states in collisions with ambient at-
instantaneous and short-lived nature of the factor of 2                                                                  mospheric constituents is much slower than vibrational
increase in the nightside 1304 ˚ and 1356 ˚ emissions
                                A           A              Neutral Densities Retrieved from                              relaxation within a single electronic state. In contrast,
suggests an ENA source, while the delay in the smaller       Dayglow Observed by the Low                                 state-resolved kinetics studies at SRI [3] show that elec-
dayside emission enhancement is more ambiguous. This                                                                     tronic mixing can be very fast and sometimes provides
delay may be a result of a drift time for ring current
                                                             Resolution Airglow and Aurora                               the mechanism for vibrational relaxation.
particles which lead to ENA production, or it may be         Spectrograph (LORAAS) aboard                                    Another source of understanding is the intensity
a thermospheric response time to geomagnetic heating         ARGOS                                                       of oxygen molecule nightglow emission from the at-
and tides. Modeling of the OI 1304 ˚ emission suggests
                                    A                                                                                    mospheres of Earth and Venus. On both planets the
a 50% increase in the MSIS densities of all species at                                                                   observed O2 (a-X) 1.27 µ emission intensity approxi-
low latitude s is needed to reproduce the dayside mea-      S A Budzien1 (202-767-9372; sab@tip.nrl.navy.mil);           mately matches the total calculated column-integrated
                                                                                                                         rate of oxygen atom recombination. Emissions from the
surement. By comparing changes in the OI lines and            K F Dymond1; S E Thonnard1; A C Nicholas1; R
N2 LBH bands, we will determine the O/N2 density                                                                         O2 (c,A’,A) Herzberg states are strongly quenched in
                                                              P McCoy2; R J Thomas3                                      both atmospheres, but when the observed intensities
ratio to evaluate possible composition changes and the
implications for a dayside ENA emission source.             1 E O Hulburt Center for Space Research , Code 7623          are adjusted for quenching, the summed rate of pro-
                                                               Naval Research Laboratory, Washington, DC 20375-          duction of population in the Herzberg states again ap-
                                                               5352, United States                                       proximately matches the total oxygen atom recombina-
                                                                                                                         tion. From the corrected intensity of the oxygen Atmo-
                                                                                                                         spheric Band emission on Earth we conclude that O2 (b)
SA52A-05 1330h POSTER                                       2 Office of Naval Research, Code 321SR 800 N Quincy
                                                                                                                         is produced in approximately 10% of recombination re-
                                                               St, Alexandria, VA 22217, United States
                                                                                                                         actions. Of course, the ground electronic state O2 (X) is
Analysis of Optical Spectra of High                         3 New Mexico Inst. Mining and Technology, Dept. of           eventually produced in every recombination. We would
                                                                                                                         also argue that the weakly bound O2 (5 Πg ) state is the
 Altitude N+ in the Polar Cap
             2
                                                               Electrical Engineering, Socorro, NM 87801, United
                                                                                                                         precursor of population in the Herzberg states [4].
                                                               States
                                                                                                                             What we have just shown is that fast collisional
 Frank Morgan 1 ((443) 778-8297;                               The Advanced Research and Global Observations Satellite   mixing and relaxation, rather than statistical weights,
   frank.morgan@jhuapl.edu)                                (ARGOS) includes several remote sensing instruments           dominate the production of electronic states following
                                                           that measure global composition, density, and temper-         oxygen atom recombination. As higher electronic states
 Jeng-Hwa Yee1 ((443) 778-6206;                            atures of the thermosphere and ionosphere. ARGOS was          are relaxed to lower ones, O + O + M → O2 (5 Πg ) →
   jeng-hwa.yee@jhuapl.edu)                                launched into a 2:30 sun-synchronous orbit on Feb. 23,        O2 (c,A’,A) → O2 (a,b) → O2 (X), the population flow
                                                           1999, and the LORAAS sensor has been monitoring               can be observed more than once, leading to a total ap-
 Gerry J. Romick1 (retired)
                                                           the upper atmospheric airglow in the far- and extreme-        parent yield that is well over 100% (about 400% in the
 1 The Johns Hopkins University Applied Physics Labo-      ultraviolet passband since May 1999. LORAAS relies            above analysis).
    ratory, 11100 Johns Hopkins Rd, Laurel, MD 20723,                                          A
                                                           upon limb scan spectra (with 17-˚ spectral resolution)            This research was supported by the NASA Geospace
    United States                                          to infer the densities of N2 , O2 , and O by inversion of     Sciences (ITM) and Planetary Atmospheres programs
                                                                        A
                                                           the OI 1356 ˚ and N2 Lyman-Birge-Hopfield emissions.          and by the NSF Atmospheric Chemistry program.
                              +
    Optical emissions from N
                              2
                                from altitudes up to at    At the 843 km altitude of ARGOS, dayglow emissions                [1] P. C. Wraight, Planet.      Space Sci. 30, 251
least 900 km have been observed by the Ultraviolet and     from thermospheric O excited by electron impact can           (1982). [2] I.W.M. Smith, Int. J. Chem. Kinetics
Visible Imagers and Spectrographic Imagers (UVISI)         be significantly contaminated by ionospheric recombi-         15, 423 (1984). [3] D. L. Huestis, R. A. Copeland,
instrument on the Midcourse Space Experiment space-        nation emission from higher altitudes. We discuss im-         and T. G. Slanger, ”Laboratory Studies of O2 Kinet-
craft. Observed emissions include the First Negative       proved algorithms for retrieving neutral densities that       ics Relevant to the Aeronomy of Earth, Venus, and
                                +                          account for this ionospheric component, and we present        Mars,” Yosemite 2000: Comparative Aeronomy in the
Bands and Meinel Bands of N . These observations
                                2                          neutral density retrievals for November 24, 1999. MSIS        Solar System (Yosemite National Park, CA, February
were taken shortly after a period of disturbed geomag-     model density estimates are compared to the HIRAAS            8-11, 2000). [4] B.-Y. Chang, D. L. Huestis, and R. A.
netic conditions, with Kp reaching 7. For example, ap-     measurements, and implications for 2-D modeling and           Copeland, ”Temperature Dependence of the Collisional
                       +                                   alternative neutral density retrieval algorithms are dis-
proximately 1 kR of N
                       2
                         First Negative 0-0 band is ob-                                                                  Removal of O2 (5 Πg ) Between 150 and 300 K,” 1999
served at 800 km altitude during one event. Results of     cussed.                                                       Spring Meeting of the American Geophysical Union
the analysis of these spectra and implications for exci-   URL: http://tipweb.nrl.navy.mil/projects/hiraas4/             (Boston, MA, June 1-4, 1999) [EOS, Trans.          AGU,
tation and polar ion outflow will be discussed.            home.htm                                                      80(17), S239 (1999)].


                                                                          This page may be freely copied.
                                                                                                                                      2000 Fall Meeting                F931
SA52A-10 1330h POSTER                                       Mars. The critical process limiting the rate of emis-       measured in dayside disk-to-limb scans. Sensitivities of
                                                            sion is excitation of CO2 in collisions with atomic         dayside 4πI(Ly α) to variations in the principal param-
                                                            oxygen: CO2 (v2 =0) + O(3 PJ ) → CO2 (v2 =1) +              eters of interest – the exobase density [H]c , the pho-
Progress in the Measurement of                                                                                          tochemically initiated upward flux φ, and the meso-
  Electron Impact Ionization Branching                      O(3 PJ ). Laboratory studies suggest rate coefficients      spheric peak density [H]peak – will be discussed for
  Ratios for Atomic Oxygen                                  of 1-2×10−12 cm3 /s while modelers prefer values in         both solar maximum and minimum conditions. Appli-
                                                            the range 3-6×10−12 .                                       cation of the RT-modeling techniques can be expected
 John P. Doering1 (410-516-7445; jdoering@jhu.edu)              We have generated potential energy surfaces for         to lead to rapid retrieval of both dayside [H]c and
                                                            CO2 -O by representing the the interactions between         φ independent of instrument calibrations, especially
                                                                                                                        when accompanied by independent determinations of
 Joseph Yang1 (4310-516-7421; jyang@jhu.edu)                the O-atom projectile and the carbon and oxygen atoms
                                                            in the target CO2 molecule by parameterization of the       [H]peak .
 1 Johns Hopkins University, Department of Chemistry
                                                            open-shell/closed-shell potential energy curves of the
    3400 N. Charles St., Baltimore, MD 21218, United        rare gas oxides [1]. This approach follows the method
    States                                                  of Diatomics in Molecules (DIM), supplemented by an
    Ionization-excitation of atomic oxygen by low en-       atoms-in-molecules treatment of spin-orbit coupling [2].


                                                                                                                                                                                     S
ergy electron impact is a process of wide interest in           The potential energy surfaces corresponding to          SA52A-15 1330h POSTER
planetary atmospheres and many astronomical objects.        CO2 (v2 =0,1) illustrate several important points.
Electron impact ionization of OI can produce O+ ions in     First, the spin-orbit splittings represent a significant
three different states: the 4 S ground state and the 2 D
and 2 P excited states. In photoionization, the branch-
ing ratios to the three states are of comparable mag-
                                                            fraction of the CO2 ν2 vibration energy. Second, the
                                                            separation between the potential energy surfaces eas-
                                                            ily spans the vibrational energy, at thermally acces-
                                                                                                                        Hot Carbon Densities and Escape
                                                                                                                         Fluxes at Mars.                                             A
                                                            sible internuclear distances. Third, the surface cross-
nitude. However, the electron impact branching ratios       ing model of Nikitin and Umanski [3] is strongly sug-
are unknown. The photoionization branching ratios are
                                                            gested. Fourth, collisions of O(3 P2 ) with CO2 (v2 =1)      Andrew F. Nagy1 (734-764-6592; anagy@umich.edu)
not applicable to electron impact ionization since pho-
                                                            can reach crossings with O(3 P0,1 ) plus CO2 (v2 =0)
toionization branching ratios are generally poor predic-                                                                 Michael W. Liemohn1 (734-763-6229;
tors of electron impact ionization branching ratios. In     with small activation energies, less than 400 cm−1 .           liemohn@umich.edu)
addition, there is no variable in photoionization which     Finally, three of the spin-orbit sublevels, one from
is comparable to the momentum change in electron im-                                                                     Jane L. Fox2 (937-775-2983;
                                                            O(3 P0 ) and two from O(3 P1 ), will be active in the
pact. We are currently engaged in an effort to mea-                                                                        fox@platmo.phy.wright.edu)
                                                            excitation direction, while six will be active in the de-
sure the branching ratios to the three final states of                                                                   Jhoon Kim3 (jkim@viva.kari.re.kr)
                                                            excitation direction, five from O(3 P2 ) and one from
the O+ ion by 100 eV electron impact ionization of
atomic oxygen. 100 eV impact energy was chosen be-          O(3 P1 ).  The finite energy separation between the          1 Space Physics Research Laboratory, Dept. of At-
cause this incident energy is near the peak of the total    crossing points from 700 to 1000 cm−1 will lead to              mos., Ocean., Space Sci., University of Michigan,
ionization cross section for OI. The method we are us-      an unexpected temperature dependence of the detailed-           Ann Arbor, Mi. 48109, United States
ing is the same that we have previously used to measure     balance relationship.
branching ratios to final states in molecular nitrogen                                                                   2 Department of Physics, Wright State University,
                                                               [1] T. H. Dunning, Jr. and P. J. Hay, J. Chem.
and oxygen. A beam of 100 eV electrons is incident          Phys. 66, 3767 (1977). [2] D. L. Huestis and N. E.              Dayton, Oh. 45435, United States
on the target atoms and the scattered incident electron     Schlotter, J. Chem. Phys. 69, 3100 (1978). [3] E. E.
and ejected secondary electron are detected in coinci-      Nikitin and S. Ya. Umanski, Faraday Disc. Chem. Soc.         3 Korean Aerospace Research Institute, 52 Eoun-Dong,
dence. Only highly asymmetric ionization events are         53, 7 (1972).                                                   Yusung-Gu, Taejon 305-333, Korea, Republic of
detected in which the scattered incident electron has
most of its original energy and the ejected secondary                                                                       The hot carbon escape fluxes and exospheric num-
electron typically has 5 eV energy. These ionization                                                                    ber densities were calculated for high and low solar ac-
events are the most common since the cross section is a     SA52A-13 1330h POSTER                                       tivity conditions at Mars. The hot carbon production
maximum for the most asymmetric ionizations and is a                                                                    sources that were considered in the calculations are i)
minimum when the two departing electrons have equal         Sensitive Cavity Ringdown Absorption                        dissociative recombination of CO2+, ii) photodissoci-
energy. Results so far have shown that the method we                                                                    ation of CO2 and iii) collisions with hot oxygen. We
are using is practical for detecting the ionization of OI
                                                              Detection of HO2 for the
                                                                                                                        used our two stream code to calculate the escape flux
and preliminary coincidence energy loss spectra have          Measurement of O + HO2 and OH +                           at the exobase and Liouvilles theorem to calculate the
been obtained. However, the experiment proceeds very          HO2 Rate Constants                                        exospheric densities.
slowly because the target species is highly reactive and
can only be produced at low density using a discharge-
                                                             Robert Robertson1 (650-859-2677;
type source.
                                                               rrobertson@crvax.sri.com)
                                                             Gregory P Smith1 (650-859-3496;
                                                                                                                        SA52A-16 1330h POSTER
SA52A-11 1330h POSTER                                          smith@mplvax.sri.com)
                                                             1 Molecular Physics Laboratory, SRI International,
Electron Impact Cross Sections for Use                         333 Ravenswood Ave., Menlo Park, CA 94025,               Fraction of Energetic Oxygen Atoms in
  in Modeling the                                              United States                                              the Upper Terrestrial Thermosphere
                                                                The failure of models to simultaneously predict
  Ionospheres/Thermospheres of the                          measured mesospheric ozone, OH, and HO2 may, ac-
  Earth and Planets                                         cording to sensitivity analysis, be largely attributable     V. Kharchenko1 (617-496-7536;
                                                            to inaccuracies in the rate constants for OH + HO2             vkharchenko@cfa.harvard.edu)
 Keeyoon Sung1 (ksung@atmsci.msrc.sunysb.edu)               and O + HO2. A program designed to accurately re-            A. Dalgarno1 (617-496-7536)
                                                            measure these rate constants at 298-220K will be de-
                                                                                                                         1 Harvard-Smithsonian Center for Astrophysics, no
 Jane L Fox1,2 (937-775-2983;                               scribed. It features computer designed photolysis ex-
   fox@platmo.phy.wright.edu)                               periments coupled with simultaneous time resolved ab-           address, Cambridge, MA 02138, United States
                                                            solute radical species concentration measurements for
 1 Marine Sciences Research Center, SUNY-Stony                                                                              The fraction of nonthermal oxygen atoms in the ter-
                                                            O, OH, and HO2. HO2 determinations using Cavity
   Brook, Stony Brook, NY 11794-5000, United States         Ringdown Absorption Spectroscopy in the near infrared       restrial thermosphere is calculated. The main sources
                                                            (1.5 um) with tunable OPO radiation will be presented,      of nascent energetic oxygen atoms are taken into ac-
 2 Department of Physics, Wright State University,
                                                            with projected sensitivities. The spectrum is compli-       count for daytime and nighttime atmospheric condi-
    Dayton, OH 45435, United States                                                                                     tions. The energy distributions of oxygen atoms are
                                                            cated by nearby water overtone absorptions, but non-
    We present our compilation of electron-impact           overlapping regions can be located.                         calculated by solving the Boltzmann kinetic equation.
cross sections for use in modeling the iono-                                                                            Rates of energy transfer collisions of energetic O atoms
spheres/thermospheres of the Earth and planets. The                                                                     with atmospheric N and O are calculated using quan-
sixteen species included are N2 , O2 , O, CO2 , CO, NO,                                                                 tal cross sections. The rate of thermalizing collisions
Ar, C, N, H, H2 , He, CH4 , C2 H2 , C2 H4 , and C2 H6 .     SA52A-14 1330h POSTER                                       is shown to be of great importance in determining the
The processes include electron-impact vibrational ex-                                                                   fraction of energetic oxygen atoms in the upper ther-
citation, electronic excitation, ionization, ionization     Retrieval of Atomic Hydrogen Densities                      mosphere.
                                                                                                                            Calculations of non-Maxwellian fraction of oxygen
and excitation, and dissociative ionization. A table for      and Fluxes from Dayside Lyman α                           atoms are performed for altitudes between 200 and 400
each species is presented that includes the processes
and the cross section references. Plots of selected cross     Limb Scanning Measurements                                km for different levels of solar activity. Results of cal-
sections are also shown.                                                                                                culations are compared with observations of hot oxygen
                                                             James Bishop (202-767-5529;                                atoms in the terrestrial atmosphere and with the results
                                                               jbishop@uap2.nrl.navy.mil)                               of previous theoretical models of hot oxygen distribu-
                                                                                                                        tions.
SA52A-12 1330h POSTER                                        Naval Research Laboratory, Code 7643, 4555 Over-
                                                              look Avenue, S.W., Washington, DC 20375, United
                                                              States
Theory of O-CO2 Collisions:
                                                                Knowledge of atomic hydrogen density distributions
  Thermospheric Cooling on Venus,                           ([H](z)) in the upper atmosphere is important both for
  Earth, and Mars                                           understanding mesospheric-lower thermospheric (MLT)
                                                            chemistry and for determining upper thermospheric-          SA52B           MC: 134             Friday 1330h
 Gert D. Billing1 (gdb@theory.ki.ku.dk)                     lower exospheric densities needed for realistic modeling
                                                            of geocoronal density and ballistic flux distributions.     Parker Lecture (See SH52A)
 David L. Huestis2 (650-859-3464;                           However, relevant data on [H] at mesospheric and ther-
    david.huestis@sri.com)                                  mospheric altitudes have remained sparse. Given the
 1 Department of Chemistry, University of Copenhagen,
                                                            prospects for improved determinations of upper atmo-        SA52B-01 1330h
                                                            spheric [H] through analysis of Lyman α airglow mea-
    Universitetsparken 5, Copenhagen 2100, Denmark          surements from several planned remote sensing satellite
                                                            missions (e.g., NASA/TIMED), it is timely to summa-
 2 Molecular Physics Laboratory, SRI International,
                                                            rize and update the method for analysis of such data.
                                                                                                                        The High Speed Solar Wind and
   333 Ravenswood Ave., Menlo Park, CA 94025,               While complicated by multiple scattering effects, ther-       Coronal Holes
   United States                                            mospheric scattering optical depths under solar max-
    Infrared emissions near 15 µ from bending-mode          imum conditions are sufficiently small (owing both to
                                                                                                                         Ian Axford (49-5556-979439; axford@linmpi.mpg.de)
vibrationally excited carbon dioxide molecules con-         decreased atomic hydrogen densities and increased tem-
trol the rates of radiative cooling in key altitude re-     peratures) that the MLT [H](z) distribution directly         Max-Planck-Institut fuer Aeronomie, Max-Planck-
gions of the upper atmospheres of Venus, Earth, and         (and strongly) impacts the Lyman α intensities (4πI)          Strasse 2, Katlenburg-Lindau 37191, Germany


                                                               This page may be freely copied.

								
To top