VIEWS: 4 PAGES: 3 POSTED ON: 12/9/2011
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 firstname.lastname@example.org); Daniel Morrison1 (240 228 4172; email@example.com); 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; firstname.lastname@example.org); 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 email@example.com); 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; firstname.lastname@example.org); 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- email@example.com) 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 firstname.lastname@example.org) and SSUSI on DMSP, produce spectral images from low Observation of Atomic Neon Emission Phil Williams2 (+44 1970 622817; email@example.com) 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 firstname.lastname@example.org) 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- email@example.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- firstname.lastname@example.org) 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 email@example.com) 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 firstname.lastname@example.org) 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 email@example.com) 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 firstname.lastname@example.org) 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 email@example.com); 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 firstname.lastname@example.org) 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 email@example.com); 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 firstname.lastname@example.org); Supriya Chakrabarti1 The High Resolution Airglow and Aurora Spec- Research Satellite (UARS) has observed ionospheric ion (617-353-5990; email@example.com); 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 firstname.lastname@example.org); Scott A Budzien2 Global Observation Satellite (ARGOS) on 23 February 1999 proton spectra. In this paper, we present the impacts (202-767-9372; email@example.com); 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 firstname.lastname@example.org); Robert P McCoy3 Low Resolution Airglow and Aurora Spectrograph (LO- and compare them with those for pure Maxwellians. (703-696-8699; email@example.com) 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 firstname.lastname@example.org) 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- email@example.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 firstname.lastname@example.org) 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  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; email@example.com); 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 . 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, firstname.lastname@example.org) (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 ) → email@example.com) 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  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).  I.W.M. Smith, Int. J. Chem. Kinetics Visible Imagers and Spectrographic Imagers (UVISI) be significantly contaminated by ionospheric recombi- 15, 423 (1984).  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).  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; firstname.lastname@example.org) 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; email@example.com) 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 . 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 . 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  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; firstname.lastname@example.org) 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 . email@example.com) 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- firstname.lastname@example.org) excitation direction, while six will be active in the de- sure the branching ratios to the three final states of Jhoon Kim3 (email@example.com) 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,  T. H. Dunning, Jr. and P. J. Hay, J. Chem. and oxygen. A beam of 100 eV electrons is incident Phys. 66, 3767 (1977).  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).  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. firstname.lastname@example.org) Gregory P Smith1 (650-859-3496; SA52A-16 1330h POSTER SA52A-11 1330h POSTER email@example.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 firstname.lastname@example.org) Keeyoon Sung1 (email@example.com) 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- firstname.lastname@example.org) 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 email@example.com) 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 (firstname.lastname@example.org) 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- email@example.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; firstname.lastname@example.org) 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.
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