Solar wind charge exchange in cometary atmospheres

III. Results from the Rosetta mission to comet 67P/Churyumov-Gerasimenko

Document identifier: oai:DiVA.org:ltu-76342
Access full text here:10.1051/0004-6361/201834881
Keyword: Engineering and Technology, Mechanical Engineering, Aerospace Engineering, Teknik och teknologier, Maskinteknik, Rymd- och flygteknik, Comets: general, Comets: individual: 67P/Churyumov-Gerasimenko, Instrumentation: detectors, Solar wind, Methods: analytical, Plasmas, Atmospheric science, Atmosfärsvetenskap
Publication year: 2019
Relevant Sustainable Development Goals (SDGs):
SDG 9 Industry, innovation and infrastructure
The SDG label(s) above have been assigned by OSDG.ai

Abstract:

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.

Authors

Cyril Simon Wedlund

Department of Physics, University of Oslo, Oslo, Norway
Other publications >>

Etienne Behar

Luleå tekniska universitet; Rymdteknik; Swedish Institute of Space Physics, Kiruna, Sweden
Other publications >>

Hans Nilsson

Luleå tekniska universitet; Rymdteknik; Swedish Institute of Space Physics, Kiruna, Sweden
Other publications >>

Markku Alho

Department of Electronics and Nanoengineering, School of Electrical Engineering, Aalto University, Aalto, Finland
Other publications >>

Esa Kallio

Department of Electronics and Nanoengineering, School of Electrical Engineering, Aalto University, Aalto, Finland
Other publications >>

Herbert Gunell

Royal Belgian Institute for Space Aeronomy, Brussels, Belgium. Department of Physics, Umeå University, Umeå, Sweden
Other publications >>

Dennis Bodewits

Physics Department, Auburn University, Auburn, USA
Other publications >>

Kevin Heritier

Department of Physics, Imperial College London, London, UK
Other publications >>

Marina Galand

Department of Physics, Imperial College London, London, UK
Other publications >>

Arnaud Beth

Department of Physics, Imperial College London, London, UK
Other publications >>

Martin Rubin

Space Research and Planetary Sciences, University of Bern, Bern, Switzerland
Other publications >>

Kathrin Altwegg

Space Research and Planetary Sciences, University of Bern, Bern, Switzerland
Other publications >>

Martin Volwerk

Space Research Institute, Austrian Academy of Sciences, Graz, Austria
Other publications >>

Guillaume Gronoff

Science directorate, Chemistry & Dynamics branch, NASA Langley Research Center, Hampton, Virginia, USA. SSAI, Hampton, Virginia, USA
Other publications >>

Ronnie Hoekstra

Zernike Institute for Advanced Materials, University of Groningen, Groningen, The Netherlands
Other publications >>

Record metadata

Click to view metadata