Energisation of O+ and O+
2 Ions at Mars: An Analysis of a 3-D Quasi-Neutral Hybrid Model Simulation |
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Authors: | E Kallio A Fedorov S Barabash P Janhunen H Koskinen W Schmidt R Lundin H Gunell M Holmström Y Futaana M Yamauchi A Grigoriev J D Winningham R Frahm J R Sharber |
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Institution: | (1) Finnish Meteorological Institute, Box 503, FIN-00101 Helsinki, Finland;(2) Centre d’Etude Spatiale des Rayonnements, BP-4346, F-31028 Toulouse, France;(3) Swedish Institute of Space Physics, Box 812, S-98 128 Kiruna, Sweden;(4) Department of Physical Sciences, University of Helsinki, P.O.Box 64, FIN-00014 Helsinki, Finland;(5) Southwest Research Institute, San Antonio, TX 7228-0510, USA;(6) Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Yoshinodai 3-1-1, Sagamihara 229-8510, Japan |
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Abstract: | We have studied the loss of O+ and O+
2 ions at Mars with a numerical model. In our quasi-neutral hybrid model ions (H+, He++, O+, O+
2) are treated as particles while electrons form a massless charge-neutralising fluid. The employed model version does not
include the Martian magnetic field resulting from the crustal magnetic anomalies. In this study we focus the Martian nightside
where the ASPERA instrument on the Phobos-2 spacecraft and recently the ASPERA-3 instruments on the Mars Express spacecraft
have measured the proprieties of escaping atomic and molecular ions, in particular O+ and O+
2 ions. We study the ion velocity distribution and how the escaping planetary ions are distributed in the tail. We also create
similar types of energy-spectrograms from the simulation as were obtained from ASPERA-3 ion measurements. We found that the
properties of the simulated escaping planetary ions have many qualitative and quantitative similarities with the observations
made by ASPERA instruments. The general agreement with the observations suggest that acceleration of the planetary ions by
the convective electric field associated with the flowing plasma is the key acceleration mechanism for the escaping ions observed
at Mars. |
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Keywords: | Mars Mars-solar wind interaction Mars Express ASPERA-3 instrument ion escape |
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