Simulation Study of Solar Wind Interaction with Mercury's Magnetosphere

International audienceThe three flybys of Mariner 10, the numerous terrestrial observations of Mercury's exosphere and the recent flybys of MESSENGER [1] have brought important information about the Hermean environment. Mercury's intrinsic magnetic field is principally dipolar and its interaction with the Solar Wind (SW) creates a small and very dynamic magnetosphere. Mercury's exosphere is a highly variable [2] and complex neutral environment made of several species : H, He, O, Na, K, Ca, and Mg have already been detected [3,4]. The small number of in situ observations and the fact that the Hermean magnetospheric activity is not observable from Earth make simulation studies of the Hermean environment a useful tool to understand the global interaction of the SW with Mercury. This study presents simulation results from a 3-dimensional parallel multi-species hybrid model of Mercury's magnetosphere interaction with the SW. The SW in this model is representative of conditions at Mercury's aphelion (0.47AU) and is composed of 95% protons and 5% alpha particles. The simulated IMF is oriented accordingly observations during the first flyby of MESSENGER on January 2008 with a cone angle of ~45°. A neutral corona of atomic hydrogen is included in this model and is partly ionized by solar photons, electron impacts and charge exchange between SW ions and neutral H. Two electron fluids with different temperature are implemented to mimic the SW and ionospheric plasma. This model is an adapted version of the 3D parallel model for the Martian environment. Planetary and SW plasmas are treated separately and the dynamic of each ion species can be investigated separately. Simulations have been performed on a grid of 190×350×350 cells with a spatial resolution of Deltax~120km. Acknowledgements The authors are indebted to CNES (French space agency) for the funding of their modeling activity through its program Sun - Heliosphere - Magnetosphere and to ANR (French national agency for research) for supporting the HELIOSARES project. References [1] Anderson, B. J., Acuna, M. H., Korth, H., Purucker, M. E., Johnson, C. L., Slavin, J. A., Solomon, S. C. and McNutt, R. L.: The Structure of Mercury's Magnetic Field from MESSENGER's First Flyby, Science, Vol. 321, pp. 82-, 2008 [2] Leblanc, F., Doressoundiram, A., Schneider, N., Mangano, V., López Ariste, A., Lemen, C., Gelly, B., Barbieri, C., remonese, G. : High latitude peaks in Mercury's sodium exosphere: Spectral signature using THEMIS solar telescope, Geophysical Research Letters, Vol. 35, L18204, 2008 [3] Leblanc, F. and Doressoundiram, A. : Mercury exosphere. II. The sodium/potassium ratio, Icarus, Vol. 211, pp. 10-20, 2011 [4] Potter, A. and Morgan, T. : Discovery of sodium in the atmosphere of Mercury, Science, Vol. 229, pp. 651-653, 198