HR: 1340h
AN: SM43A-1070    [Abstracts]
TI: Bifurcation and hysteresis of the magnetospheric structure with a varying Southward IMF: golbal 3D full particle simulations
AU: * Li, W
EM: liwei@aoi3.cs.tsukuba.ac.jp
AF: University of Tsukuba, 1-1-1 Ten-nou-dai, Tsukuba, 305-8573, Japan
AU: Cai, D
EM: cai@cs.tsukuba.ac.jp
AF: University of Tsukuba, 1-1-1 Ten-nou-dai, Tsukuba, 305-8573, Japan
AU: Lembege, B
EM: lembege@cetp.ipsl.fr
AF: CETP/IPSL, Avenue Europe, Velizy, 78140, France
AU: Nishikawa, K
EM: Ken-Ichi.Nishikawa@nsstc.nasa.gov
AF: NSSTC, Sparkman Drive, Huntsville, 35805, United States
AB: Using a three-dimensional full electromagnetic particle model (EMPM), we have performed global simulations of the interaction between the solar wind and the terrestrial magnetosphere, and have investigated its asymptotic stability. The distance between the dayside magnetopause subsolar point and the earth center, Rmp , is measured, as the intensity of southward IMF Bz is slowly varying. Based on the field topology theory, one analyzes the variation of Rmp as a reference index of the dynamics of this interaction, when IMF Bz successively increases and decreases to its original value. Two striking results are observed. First, as the IMF Bz increases above a critical value, the variation of Rmp suddenly changes (so called "bifurcation" process in field topology). For this critical value, the overall magnetic field topology changes drastically and is identified as being the signature of magnetic reconnection at the subsolar point on the magnetopause. Second, this subsolar point recovers its original location Rmp by following different paths as the IMF Bz value increases (from zero to a maximum fixed value) and decreases (from this maximum to zero) passing through some critical values. These different paths are the signature of an "hysteresis" effect, and are characteristic of the so-called "subcritical-type" bifurcation. This hysteresis signature indicates that dissipation processes take place via an energy transfer from the solar wind to the magnetosphere by some irreversible way, which leads to a drastic change in the magnetospheric field topology. This hysteresis is interpreted herein as a consequence of the magnetic reconnection taking place at the dayside magnetopause. The field topology reveals to be a very powerful tool to analyze the signatures of three-dimensional magnetic reconnection without the obligation for determining the mechanisms responsible for, and the consequences of the reconnection on the overall magnetospheric dynamics.
DE: 2723 Magnetic reconnection (7526, 7835)
DE: 2753 Numerical modeling
DE: 2790 Substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting