Geomagnetic Storm and Interplanetary Shock

概要

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The solar wind-magnetosphere interaction is studied to clarify its most important role, that of regulating the development of geomagnetic storms in relation to the physical solar wind parameters carried with the interplanetary shock. This has been carried out on the basis of the data of the solar wind plasma and the interplanetary magnetic field (IMF) measured by the ISEE-3 satellite. The most important result in the present study is that the strong interplanetary shock is not a necessary condition for yielding a great geomagnetic storm. A great geomagnetic storm is caused by a sustained large southward IMF (B_z) carried with the interplanetary shock. The sustained southward B_z does not always directly accompany the onset of the shock. It is, however, frequently accompanied by several types of discontinuity contained in the shock. These discontinuities play an important role on the southward turning of B_z, which most effectively regulates the geomagnetic storm. A prediction of the Dst value of the storm main phase is proposed by constructing a new index, which can be produced by a summation of the multiplied two solar wind parameters, i. e., duration of a B_z (hours) with the same polarity, and its intensity. This new index is highly correlative with the peak D_<st> value of the geomagnetic storm main phase.
東海大学の論文