1Department of Physics & Astronomy, University of Leicester, Leicester LE1 7RH, UK
2Institute for Geophysics and Extraterrestrial Physics, TU Braunschweig, Germany
3Swedish Institute of Space Physics, Kiruna, Sweden
4Institute for Theoretical Physics, TU Braunschweig, Germany
5Space Sciences Laboratory, University of California, Berkeley, USA
6Southwest Research Institute, San Antonio, USA
7The Blackett Laboratory, Imperial College London, London, UK
8Department of Physics and Astronomy, University of Iowa, Iowa City, USA
9Swedish Institute of Space Physics, Uppsala, Sweden
10Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany
11CETP-IPSL, 10–12 avenue de l'Europe, 78140 Velizy, France
12Laboratoire de Physique et Chimie de l'Environnement, Orléans, France
Received: 16 Jun 2009 – Revised: 26 Oct 2009 – Accepted: 07 Dec 2009 – Published: 17 Dec 2009
Abstract. We report on new simultaneous in-situ observations at Mars from Rosetta and Mars Express (MEX) on how the Martian plasma environment is affected by high pressure solar wind. A significant sharp increase in solar wind density, magnetic field strength and turbulence followed by a gradual increase in solar wind velocity is observed during ~24 h in the combined data set from both spacecraft after Rosetta's closest approach to Mars on 25 February 2007. The bow shock and magnetic pileup boundary are coincidently observed by MEX to become asymmetric in their shapes. The fortunate orbit of MEX at this time allows a study of the inbound boundary crossings on one side of the planet and the outbound crossings on almost the opposite side, both very close to the terminator plane. The solar wind and interplanetary magnetic field (IMF) downstream of Mars are monitored through simultaneous measurements provided by Rosetta. Possible explanations for the asymmetries are discussed, such as crustal magnetic fields and IMF direction. In the same interval, during the high solar wind pressure pulse, MEX observations show an increased amount of escaping planetary ions from the polar region of Mars. We link the high pressure solar wind with the observed simultaneous ion outflow and discuss how the pressure pulse could also be associated with the observed boundary shape asymmetry.
Edberg, N. J. T., Auster, U., Barabash, S., Bößwetter, A., Brain, D. A., Burch, J. L., Carr, C. M., Cowley, S. W. H., Cupido, E., Duru, F., Eriksson, A. I., Fränz, M., Glassmeier, K.-H., Goldstein, R., Lester, M., Lundin, R., Modolo, R., Nilsson, H., Richter, I., Samara, M., and Trotignon, J. G.: Rosetta and Mars Express observations of the influence of high solar wind pressure on the Martian plasma environment, Ann. Geophys., 27, 4533-4545, doi:10.5194/angeo-27-4533-2009, 2009.