JpGU-AGU Joint Meeting 2017

講演情報

[EJ]Eveningポスター発表

セッション記号 P (宇宙惑星科学) » P-CG 宇宙惑星科学複合領域・一般

[P-CG24] [EJ] 惑星大気圏・電磁圏

2017年5月21日(日) 17:15 〜 18:30 ポスター会場 (国際展示場 7ホール)

[PCG24-P07] Variations of ion escape from the past to present at Mars

*堺 正太朗1関 華奈子1寺田 直樹2田中 高史3,4品川 裕之5 (1.東京大学大学院理学系研究科、2.東北大学大学院理学研究科、3.九州大学、4.REPPUコード研究所、5.情報通信研究機構)

キーワード:Mars, Ion escape, Atmospheric escape

The present Mars has thin atmosphere consisting mainly of CO2 and does not have liquid water at the surface. The recent space missions gave some evidences for existence of liquid water in the past Mars. It suggests that Mars have experienced atmospheric loss from the past through present. One of the important mechanisms of atmospheric escape is the ion loss. The ion escape is largely controlled by the magnetic configuration, solar wind and solar XUV (X-ray and extreme ultraviolet) irradiances. Terada et al. (2009) showed that the ion escape rate was at most five orders of magnitude higher under the past active solar condition than under the present ones.

The magnetic field is also an important factor in determining the ion escape rate. The present Mars does not have intrinsic global magnetic field, but is leaving the magnetism in its crust, which is known as the crustal magnetic field. The existence of crustal field suggests that Mars had a global magnetic field of interior origin in the past and the different escape mechanism from the present. The magnitude was perhaps about 0.1 G which is corresponding to the strength of the present magnetic field of the Earth's surface (Curtis and Ness, 1988).

We present the ion escape rates calculated by different magnetic configurations and solar conditions, and compare the results with the Terada et al. (2009) ones. The three-dimension and multi-species magnetohydrodynamics (MHD) modeling are used for the simulation. We will discuss the variation of escape rate due to the differences of magnitude of magnetic field, solar XUV irradiances, and solar wind density.

References
Curtis, S. A., and N. F. Ness (1988), Remanent magnetism at Mars, Geophys. Res. Lett., 15, 737-739, doi:10.1029/GL015i008p00737.
Terada, N., et al. (2009), Atmosphere and water loss from early Mars under extreme solar wind and extreme ultraviolet conditions, Astrobiology, 9, 55-70, doi:10.1089/ast.2008.0250.