Development of Magnetic Topology During the Growth Phase of the Substorm Inducing the Onset of the Near-Earth Neutral Line

T. Tanaka, Y. Ebihara, M. Watanabe, M. Den, S. Fujita, T. Kikuchi, K. K. Hashimoto, R. Kataoka

研究成果: Contribution to journalArticle査読

5 被引用数 (Scopus)

抄録

The transition of magnetic topology is analyzed during the substorm. During the growth phase in the polar ionosphere, magnetic fields consist of three categories: closed magnetic field, open magnetic field leading to the northward interplanetary magnetic field (IMF), and open field leading to the southward IMF. While the open magnetic field region leading to the southward IMF expands consistently during the growth phase, the ionospheric onset starts inside the closed field line region. There should be triple points where three kinds of magnetic field coexist in the ionosphere. Connected to the triple points, complex magnetic topologies appear in the magnetosphere. There occur definitive changes in the global magnetic topology such as retreat of cusp nulls generated under the northward IMF, generation of plasma sheet magnetic fields with reverse curvature, generation of bifurcation areas on the magnetopause, formation of new dayside nulls, development of null lines on the flank, and generation of bifurcation areas (group of nulls) on the magnetopause. During the late growth phase, divergence Vx flow is excited in the central plasma sheet associated with the appearance of reverse curvature. The plasma sheet reconnection starts 5 min before the ionospheric onset from a localized area at X = −17.5 Re due to the reduction of the normal component Bz caused by divergence Vx flow. It occurs in the residual magnetic structure formed under the northward IMF as a three-dimensional reconnection with a guide field By. The resulting two-turn coil of magnetic field forms a plasmoid, which is ejected downtail.

本文言語英語
ページ(範囲)5158-5183
ページ数26
ジャーナルJournal of Geophysical Research: Space Physics
124
7
DOI
出版ステータス出版済み - 2019

All Science Journal Classification (ASJC) codes

  • 宇宙惑星科学
  • 地球物理学

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