Effects of the surface conductivity and the IMF strength on the dynamics of planetary ions in Mercury's magnetosphere

Abstract : To examine the effects of planetary surface conductivity and the southward IMF strength on ion dynamics, systematic trajectory tracings of Na+ ions were performed in the electric and magnetic field configurations obtained from magnetohydrodynamics (MHD) simulations of the solar wind-Mercury interaction. Comparison with a previous study, which used an analytical model that rescaled the Earth's magnetosphere and assumed the existence of the distant neutral line (DNL) in Mercury's magnetotail, shows a drastic change in the Na+ precipitation pattern onto due to the formation of the near-Mercury neutral line (NMNL) in MHD simulations. The Na+ precipitation band at approximately 30 degrees of latitude (LAT), which was obtained in the previous study, disappeared in the equivalent low-conductivity MHD case due to the NMNL formation, while the NMNL formation causes high-energy Na+ precipitation in the equatorial region. The change in strength of the southward IMF (sBz) alters the location of the NMNL and the Na+ precipitation pattern. In the low-conductivity sBz = 5 case, both the equatorial precipitation and the Na+ band at approximately LAT = 30 are formed. In the high-conductivity sBz = 5 case, magnetospheric convection through the polar regions is suppressed, which results in a region of dense Na+ near the planet. These results suggest that the precipitation pattern of planetary ions onto Mercury's surface changes significantly with the activity level of Mercury's magnetosphere. It is also suggested that observations of the magnetospheric convection, the distribution of Na+ ions around the planet, or the precipitation pattern of Na+ ions onto the planetary surface can provide us information about the surface conductivity.
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Journal of Geophysical Research : Space Physics, American Geophysical Union/Wiley, 2013, 118 (6), pp.3233-3242. 〈10.1002/jgra.50181〉
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Soumis le : jeudi 11 avril 2013 - 10:27:45
Dernière modification le : mercredi 19 septembre 2018 - 01:28:41

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Kanako Seki, Naoki Terada, Manabu Yagi, Dominique C. Delcourt, François Leblanc, et al.. Effects of the surface conductivity and the IMF strength on the dynamics of planetary ions in Mercury's magnetosphere. Journal of Geophysical Research : Space Physics, American Geophysical Union/Wiley, 2013, 118 (6), pp.3233-3242. 〈10.1002/jgra.50181〉. 〈hal-00811799〉

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