日本地球惑星科学連合2018年大会

講演情報

[EE] ポスター発表

セッション記号 P (宇宙惑星科学) » P-EM 太陽地球系科学・宇宙電磁気学・宇宙環境

[P-EM12] Space Weather, Space Climate, and VarSITI

2018年5月24日(木) 10:45 〜 12:15 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ:片岡 龍峰(国立極地研究所)、Antti A Pulkkinen (NASA Goddard Space Flight Center)、草野 完也(名古屋大学宇宙地球環境研究所、共同)、塩川 和夫(名古屋大学宇宙地球環境研究所)

[PEM12-P04] IMF dependence on solar wind plasma

*荒木 徹

キーワード:IMF、Dst index、solar wind plasma

It is usually believed that IMF is determined independently of solar wind plasma. However, the Bz component of IMF becomes smaller depending upon decrease of the solar wind dynamic pressure as shown in Figure A. This property has been found from the scatter plot of Dst index versus the square root of solar wind dynamic pressure (Pd^0.5, Figure B). There are two boundaries in Figure B. The upper boundary which linearly increases with increasing Pd^0.5 shows the minimum level of the ring current. For a fixed value of Pd, Dst (ring current) decreases with decreasing negative Bz. The lower boundary which linearly decreases with increasing Pd^0.5 is produced by decreasing negative IMF- Bz seen in Figure A. The scatter plot of Dst index versus the square root of the solar wind density (N^0.5) shows the similar pattern as Figure B. When Pd or N becomes smaller, IMF-Bz approaches to zero value while the Bx- and By-component converges to a finite value of 3-4 nT. This means that IMF shows a typical spiral pattern for rare solar wind.