| Summary: | 博士 === 國立中央大學 === 太空科學研究所 === 101 === A statistic study of one-dimensional (1D) and two-dimensional (2D) structure of Earth’s magnetopause is carried out by analyzing AMPTE/IRM and THEMIS plasma and magnetic field data. The analyses are based on the minimum variance analysis (MVA), the deHoffmann-Teller (HT) frame analysis and the Walén relation. A total of 328 magnetopause crossings are analyzed and error estimates associated with MVA and HT fame analyses. In 142 out of 328 events both MVA and HT frame analyses yield high quality results which are classified as either tangential-discontinuity (TD) or rotational-discontinuity (RD) structures based only on the Walén relation. For high quality events, the average normal magnetic field for TDs and RDs is 4.4nT ( Bn/B=11%) and 24nT ( Bn/B=31%), respectively. We have also examined for the first time the dependence of magnetic reconnection on plasma beta difference, delta_beta , and magnetic field shear angle, theta, across the current sheet based on the theoretical relation of (where L/di is the characteristic length of current sheet in units of ion inertial length) recently proposed by Swisdak et al. [2010] as the necessary condition for the occurrence of magnetic reconnection. The plasma conditions adjacent to Earth’s magnetopause are examined for 846 magnetopause crossing events from AMPTE and THEMIS spacecraft. It is found that 93% of RDs and 72% of TDs fall in the reconnection regime bounded by delta-beta curve. This result implies that the plasma condition of Earth’s magnetopause is in favor for reconnection. While RD events occur only for delta_beta<2.8 and events with Swa~1 occur only for delta_beta<1. Two-dimensional Grad-Shafranov (GS) reconstruction scheme is developed and applied to a large of number of TD and RD events which shows similar reconnection feature with single or multiple X-line accompanied with magnetic islands.
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