Solar wind charge exchange in cometary atmospheres III. Results from the Rosetta mission to comet 67P/Churyumov-Gerasimenko

被引：22

作者：

Wedlund, Cyril Simon ^{[1
]}

Behar, Etienne ^{[2
,3
]}

Nilsson, Hans ^{[2
,3
]}

Alho, Markku ^{[4
]}

Kallio, Esa ^{[4
]}

Gunell, Herbert ^{[5
,6
]}

Bodewits, Dennis ^{[7
]}

Heritier, Kevin ^{[8
]}

Galand, Marina ^{[8
]}

Beth, Arnaud ^{[8
]}

Rubin, Martin ^{[9
]}

Altwegg, Kathrin ^{[9
]}

Volwerk, Martin ^{[10
]}

Gronoff, Guillaume ^{[11
,12
]}

Hoekstra, Ronnie ^{[13
]}

机构：

[1] Univ Oslo, Dept Phys, POB 1048, N-0316 Oslo, Norway

[2] Swedish Inst Space Phys, POB 812, S-98128 Kiruna, Sweden

[3] Lulea Univ Technol Elect & Space Engn, Dept Comp Sci, S-98128 Kiruna, Sweden

[4] Aalto Univ, Sch Elect Engn, Dept Elect & Nanoengn, POB 15500, Aalto 00076, Finland

[5] Royal Belgian Inst Space Aeron, Ave Circulaire 3, B-1180 Brussels, Belgium

[6] Limed Univ, Dept Phys, S-90187 Umea, Sweden

[7] Auburn Univ, Phys Dept, Auburn, AL 36849 USA

[8] Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England

[9] Univ Bern, Space Res & Planetary Sci, CH-3012 Bern, Switzerland

[10] Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria

[11] NASA, Langley Res Ctr, Sci Directorate, Chem & Dynam Branch, Hampton, VA 23666 USA

[12] SSAI, Hampton, VA 23666 USA

[13] Univ Groningen, Zernike Inst Adv Mat, Nijenborgh 4, NL-9747 AG Groningen, Netherlands

来源：

ASTRONOMY & ASTROPHYSICS | 2019年 / 630卷

关键词：

comets: general; comets: individual: 67P/Churyumov-Gerasimenko; instrumentation: detectors; solar wind; methods: analytical; plasmas; ION-CYCLOTRON WAVES; 67P; PLASMA; ANALYZER; ATOMS;

D O I：

10.1051/0004-6361/201834881

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

Context. Solar wind charge-changing reactions are of paramount importance to the physico-chemistry of the atmosphere of a comet. The ESA/Rosetta mission to comet 67P/Churyumov-Gerasimenko (67P) provides a unique opportunity to study charge-changing processes in situ. Aims. To understand the role of these reactions in the evolution of the solar wind plasma and interpret the complex in situ measurements made by Rosetta, numerical or analytical models are necessary. Methods. We used an extended analytical formalism describing solar wind charge-changing processes at comets along solar wind streamlines. The model is driven by solar wind ion measurements from the Rosetta Plasma Consortium-Ion Composition Analyser (RPC-ICA) and neutral density observations from the Rosetta Spectrometer for Ion and Neutral Analysis-Comet Pressure Sensor (ROSINA-COPS), as well as by charge-changing cross sections of hydrogen and helium particles in a water gas. Results. A mission-wide overview of charge-changing efficiencies at comet 67P is presented. Electron capture cross sections dominate and favor the production of He and H energetic neutral atoms (ENAs), with fluxes expected to rival those of H+ and He2+ ions. Conclusions. Neutral outgassing rates are retrieved from local RPC-ICA flux measurements and match ROSINA estimates very well throughout the mission. From the model, we find that solar wind charge exchange is unable to fully explain the magnitude of the sharp drop in solar wind ion fluxes observed by Rosetta for heliocentric distances below 2.5 AU. This is likely because the model does not take the relative ion dynamics into account and to a lesser extent because it ignores the formation of bow-shock-like structures upstream of the nucleus. This work also shows that the ionization by solar extreme-ultraviolet radiation and energetic electrons dominates the source of cometary ions, although solar wind contributions may be significant during isolated events.

引用

页数：15

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