Japan Geoscience Union Meeting 2018

Presentation information

[EE] Poster

P (Space and Planetary Sciences) » P-EM Solar-Terrestrial Sciences, Space Electromagnetism & Space Environment

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

Thu. May 24, 2018 10:45 AM - 12:15 PM Poster Hall (International Exhibition Hall7, Makuhari Messe)

convener:Ryuho Kataoka(National Institute of Polar Research), Antti A Pulkkinen (NASA Goddard Space Flight Center), Kanya Kusano(名古屋大学宇宙地球環境研究所, 共同), Kazuo Shiokawa(Institute for Space-Earth Environmental Research, Nagoya University)

[PEM12-P04] IMF dependence on solar wind plasma

*Tohru Araki

Keywords: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.