太阳风在地球激波前兆区减速的统计研究

本文首次利用完全相同两颗卫星（CLUSTER C1和C3）的数据对地球激波前兆区太阳风的减速和偏转特性进行了统计研究.结果表明，在激波前兆坐标系中，太阳风减小的速度随观测点到激波的距离D_BS增大而减小，随行星际磁场与激波法向夹角θ_BN增大也减小，在ULF波动区深度D_WS小于6R_e(R_e为地球半径)的范围内最为显著；伴随着太阳风减速的另外一个现象——太阳风的偏转，也存在相似的规律.其最大减速和最大偏转角度分别为10 km/s和3°.太阳风减速和偏转，以及随之变化的太阳风动压，可能会引起地球磁层顶位置和形状发生改变，同时也为激波前兆区弥散（diffuse）离子的起源及加热提供了一种可能的机制.

Statistical study of the solar wind deceleration in the Earth's foreshock region

The data from two same satellites (CLUSTER C1 and C3) were used to make a statistical study of the solar wind deceleration and deflection in the Earth′s foreshock region for the first time. In the foreshock coordinates, the magnitude of deceleration is inversely proportional to D_BS measuring the distance between the satellite and the bow shock along the interplanet magnetic field (IMF), and also inversely proportional to θ_BN （the angle between the IMF and the bow shock normal）. The decelerations mainly occur when D_WS (the distance from satellite to the ULF wave boundary along X direction) is less than 6R_e. On the other hand, the solar wind deflection, displays a similar feature. The largest values of deceleration and deflection are, respectively, estimated as 10 km/s and 3°. These decelerations and deflections not only lead to a variation of the magnetopause′s position and shape, but also supplies a possible generation mechanism of the diffuse ions in the foreshock region.