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_C 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.