Photoelectrons as a Tracer of Planetary Atmospheric Composition: Application to CO on Mars

被引：20

作者：

Wu, X. -S. ^{[1
,2
]}

Cui, J. ^{[2
,3
,4
]}

Yelle, R. V. ^{[5
]}

Cao, Y. -T. ^{[1
,4
]}

He, Z. -G. ^{[2
,3
]}

He, F. ^{[6
,7
]}

Wei, Y. ^{[6
,7
]}

机构：

[1] Chinese Acad Sci, Natl Astron Observ, Beijing, Peoples R China

[2] Chinese Acad Sci, Ctr Excellence Comparat Planetol, Hefei, Anhui, Peoples R China

[3] Sun Yat Sen Univ, Sch Atmospher Sci, Planetary Environm & Astrobiol Res Lab PEARL, Zhuhai, Guangdong, Peoples R China

[4] Univ Chinese Acad Sci, Sch Astron & Space Sci, Beijing, Peoples R China

[5] Univ Arizona, Lunar & Planetary Sci Lab, Tucson, AZ USA

[6] Chinese Acad Sci, Inst Geol & Geophys, Beijing, Peoples R China

[7] Univ Chinese Acad Sci, Sch Earth & Planetary Sci, Beijing, Peoples R China

来源：

JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS | 2020年 / 125卷 / 07期

基金：

美国国家科学基金会;

关键词：

photoelectron; atmospheric composition; PHOTOIONIZATION CROSS-SECTIONS; SINGLE-PHOTOIONIZATION; ELECTRON COLLISIONS; IONIC FRAGMENTATION; IONOSPHERE; IMPACT;

D O I：

10.1029/2020JE006441

中图分类号：

P3 [地球物理学]; P59 [地球化学];

学科分类号：

0708 ; 070902 ;

摘要：

Photoelectrons are an extensively studied component of planetary ionospheres which have been frequently used as a diagnostic of ambient magnetic fields. We show in this study that they also provide information on atmospheric composition via the altitude variation of photoelectron intensity at specific energies. Such an idea is applied to Mars for which a large observational sample of photoelectrons is available from the Solar Wind Electron Analyzer measurements made by the Mars Atmosphere and Volatile Evolution (MAVEN). Our analysis reveals a strong decline in photoelectron intensity from 160 to 200 km, but this trend is restricted to a narrow energy range of 10-15 eV. By employing analytical yield spectrum calculations, we derive the model variations based on different choices of the background atmosphere. We find that the presence of CO is crucial for reproducing the observed variations. This allows atmospheric CO densities to be estimated from photoelectron measurements, which are a factor of 3-7 lower than the published densities based on the MAVEN Neutral Gas and Ion Mass Spectrometer measurements and in better agreement with existing model results. In general, the usefulness of photoelectron intensity at a specific energy as a tracer of atmospheric composition relies critically on the species-dependent inelastic electron impact cross section at this energy. Plain Language Summary On each solar system body with a substantial atmosphere, the ionization of atmospheric neutrals by solar photons produces photoelectrons at a typical energy of several eV to several hundred eV. These electrons have caught extensive research interests for decades because their spatial distribution has been recognized as a good tracer of ambient magnetic fields. In this study, we propose that photoelectrons could also be used as a tracer of atmospheric composition. Such an idea is applied to Mars, showing that the change of photoelectron flux with altitude at 10-15 eV relies critically on the distribution of atmospheric CO. When applied to other planets, the combination of the atmospheric species and photoelectron energy involved may vary, depending on the detailed characteristics of inelastic collisions between electrons and neutrals. Our idea provides a potentially useful constraint on the abundance of key atmospheric species when it cannot be measured accurately by a mass spectrometer, a situation often encountered in modern planetary missions.

引用

页数：11

共 49 条

[1] Monte Carlo model of electron energy degradation in a CO2 atmosphere [J].

Bhardwaj, Anil ;

Jain, Sonal Kumar .

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 2009, 114

[2] Electron-molecule scattering cross-sections. I. Experimental techniques and data for diatomic molecules [J].

Brunger, MJ ;

Buckman, SJ .

PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS, 2002, 357 (3-5) :215-458

[3] Field-Aligned Photoelectron Energy Peaks at High Altitude and on the Nightside of Titan [J].

Cao, Y. -T. ;

Wellbrock, A. ;

Coates, A. J. ;

Caro-Carretero, R. ;

Jones, G. H. ;

Cui, J. ;

Galand, M. ;

Dougherty, M. K. .

JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS, 2020, 125 (01)

[4] Study of the Martian cold oxygen corona from the OI 130.4nm by IUVS/MAVEN [J].

Chaufray, J. Y. ;

Deighan, J. ;

Chaffin, M. S. ;

Schneider, N. M. ;

McClintock, W. E. ;

Stewart, A. I. F. ;

Jain, S. K. ;

Crismani, M. ;

Stiepen, A. ;

Holsclaw, G. M. ;

Clarke, J. T. ;

Montmessin, F. ;

Eparvier, F. G. ;

Thiemann, E. M. B. ;

Chamberlin, P. C. ;

Jakosky, B. M. .

GEOPHYSICAL RESEARCH LETTERS, 2015, 42 (21) :9031-9039

[5] Ionospheric photoelectrons at Venus:: Initial observations by ASPERA-4 ELS [J].

Coates, A. J. ;

Frahm, R. A. ;

Linder, D. R. ;

Kataria, D. O. ;

Soobiah, Y. ;

Collinson, G. ;

Sharber, J. R. ;

Winningham, J. D. ;

Jeffers, S. J. ;

Barabash, S. ;

Sauvaud, J. -A. ;

Lundin, R. ;

Holmstrom, M. ;

Futaana, Y. ;

Yamauchi, M. ;

Grigoriev, A. ;

Andersson, H. ;

Gunell, H. ;

Fedorov, A. ;

Thocaven, J. -J. ;

Zhang, T. L. ;

Baumjohann, W. ;

Kallio, E. ;

Koskinen, H. ;

Kozyra, J. U. ;

Liemohn, M. W. ;

Ma, Y. ;

Galli, A. ;

Wurz, P. ;

Bochsler, P. ;

Brain, D. ;

Roelof, E. C. ;

Brandt, P. ;

Krupp, N. ;

Woch, J. ;

Fraenz, M. ;

Dubinin, E. ;

McKenna-Lawlor, S. ;

Orsini, S. ;

Cerulli-Irelli, R. ;

Mura, A. ;

Milillo, A. ;

Maggi, M. ;

Curtis, C. C. ;

Sandel, B. R. ;

Hsieh, K. C. ;

Szego, K. ;

Asamura, A. ;

Grande, M. .

PLANETARY AND SPACE SCIENCE, 2008, 56 (06) :802-806

[6] Ionospheric electrons in Titan's tail: Plasma structure during the cassini T9 encounter [J].

Coates, A. J. ;

Crary, F. J. ;

Young, D. T. ;

Szego, K. ;

Arridge, C. S. ;

Bebesi, Z. ;

Sittler, E. C., Jr. ;

Hartle, R. E. ;

Hill, T. W. .

GEOPHYSICAL RESEARCH LETTERS, 2007, 34 (24)

[7] Distant ionospheric photoelectron energy peak observations at Venus [J].

Coates, A. J. ;

Wellbrock, A. ;

Frahm, R. A. ;

Winningham, J. D. ;

Fedorov, A. ;

Barabash, S. ;

Lundin, R. .

PLANETARY AND SPACE SCIENCE, 2015, 113 :378-384

[8] Ionospheric photoelectrons: Comparing Venus, Earth, Mars and Titan [J].

Coates, A. J. ;

Tsang, S. M. E. ;

Wellbrock, A. ;

Frahm, R. A. ;

Winningham, J. D. ;

Barabash, S. ;

Lundin, R. ;

Young, D. T. ;

Crary, F. J. .

PLANETARY AND SPACE SCIENCE, 2011, 59 (10) :1019-1027

[9] Nitric Oxide Abundance in the Martian Thermosphere and Its Diurnal Variation [J].

Cui, J. ;

Fu, M-H ;

Ren, Z-P ;

Gu, H. ;

Guo, J-H ;

Wu, X-S ;

Wu, Z-P ;

Lai, H-R ;

Wei, Y. .

GEOPHYSICAL RESEARCH LETTERS, 2020, 47 (09)

[10] Ionization Efficiency in the Dayside Martian Upper Atmosphere [J].

Cui, J. ;

Wu, X. -S. ;

Xu, S. -S. ;

Wang, X. -D. ;

Wellbrock, A. ;

Nordheim, T. A. ;

Cao, Y. -T. ;

Wang, W. -R. ;

Sun, W. -Q. ;

Wu, S. -Q. ;

Wei, Y. .

ASTROPHYSICAL JOURNAL LETTERS, 2018, 857 (02)

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