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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 30, issue 11
Ann. Geophys., 30, 1595-1609, 2012
https://doi.org/10.5194/angeo-30-1595-2012
© Author(s) 2012. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 30, 1595-1609, 2012
https://doi.org/10.5194/angeo-30-1595-2012
© Author(s) 2012. This work is distributed under
the Creative Commons Attribution 3.0 License.

Regular paper 27 Nov 2012

Regular paper | 27 Nov 2012

Energetic protons at Mars: interpretation of SLED/Phobos-2 observations by a kinetic model

E. Kallio1, S. McKenna-Lawlor2, M. Alho1, R. Jarvinen1, S. Dyadechkin1, and V. V. Afonin3 E. Kallio et al.
  • 1Finnish Meteorological Institute, Helsinki, Finland
  • 2Space Technology Ireland, Maynooth Co., Kildare, Ireland
  • 3Space Research Institute, Moscow, Russia

Abstract. Mars has neither a significant global intrinsic magnetic field nor a dense atmosphere. Therefore, solar energetic particles (SEPs) from the Sun can penetrate close to the planet (under some circumstances reaching the surface). On 13 March 1989 the SLED instrument aboard the Phobos-2 spacecraft recorded the presence of SEPs near Mars while traversing a circular orbit (at 2.8 RM). In the present study the response of the Martian plasma environment to SEP impingement on 13 March was simulated using a kinetic model. The electric and magnetic fields were derived using a 3-D self-consistent hybrid model (HYB-Mars) where ions are modelled as particles while electrons form a massless charge neutralizing fluid. The case study shows that the model successfully reproduced several of the observed features of the in situ observations: (1) a flux enhancement near the inbound bow shock, (2) the formation of a magnetic shadow where the energetic particle flux was decreased relative to its solar wind values, (3) the energy dependency of the flux enhancement near the bow shock and (4) how the size of the magnetic shadow depends on the incident particle energy. Overall, it is demonstrated that the Martian magnetic field environment resulting from the Mars–solar wind interaction significantly modulated the Martian energetic particle environment.

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