[P-PS04] 火星と火星圏の科学

[PPS04-04] The Induced Global Looping Magnetic Field on Mars

*Lihui Chai¹、Weixing Wan¹、Yong Wei¹、Tielong Zhang²、Willi Exner³、Markus Fraenz⁴、Eduard Dubinin⁴、Moritz Feyerabend³、Uwe Motschmann³、Yingjuan Ma⁵、J. S. Halekas⁶ (1.Institute of Geology and Geophysics Chinese Academy of Sciences、2.Space Research Institute, Austrian Academy of Sciences, Graz, Austria、3.Institute for Theoretical Physics, TU Braunschweig, Braunschweig, Germany、4.Max Planck Institute for Solar System Research, Goettingen, Germany、5.Institute of Geophysics and Planetary Physics, University of California, Los Angeles, Los Angeles, CA, USA、6.Department of Physics and Astronomy, University of Iowa, Iowa City, IA, USA)

キーワード：Mars, Venus, induced magnetosphere, looping magnetic field

Magnetic fields inconsistent with draped IMFs and crustal fields have been observed on Mars. Considering the discovery of a global looping magnetic field around the Venusian magnetotail and the similarities in the solar wind interactions between Mars and Venus, we use MAVEN observations to investigate the global looping field on Mars and its formation mechanism. It is found that a global looping field also exists on Mars; therefore, this type of global looping field is a common feature of unmagnetized planetary bodies with ionospheres and it should also exist on Titan and near-Sun comets. The comparison of the looping fields on Mars and Venus shows that the looping field is stronger on Mars. Solar wind azimuthal flows around the magnetotail towards the -E magnetotail polar region (X_MSE<0,Y_MSE=0,Z_MSE}<-1R_M) are observed. We illustrate that the looping field can be formed by bending the draped field lines with these azimuthal flows, and that these azimuthal flows are associated with heavy ion plumes along the +E direction that are expected to be stronger on Mars than Venus. The current system associated with the looping field and its possible connection with the nightside ionosphere formations and ion escapes on Mars and Venus are discussed.