The Study Of Braking Of High-speed Flows In The Near-tail And The Remote-tail Responds To The Extreme Interplanetary Conditions

The deceleration processes of plasma sheet high-speed flows have great significance to magnetospheric particle acceleration, magnetic field perturbation,magnetic flux transport, triggering of substorm, and the current system formation in the magnetotail. The magnetopause is one of the most important parameters in space physics for the understanding of the solar wind-magnetosphere coupling. This paper shows the magnetotail deceleration region of the high-speed flows, and magnetopause location in response to extreme solar wind and characteristic of the low latitude boundary layer, we have obtained some new results and interpretations.The main research and conclusion are as follows:First, THEMIS data are used to investigate the substroms. Two satellites of the THEMIS mission (THA and THE), were often separated largely in Zdirection, but had small X and Y separations from February to April in 2009. Such special configuration allows simultaneous observations of high-speed flows at the center of the plasma sheet and plasma sheet boundary layer. Based on selected case study and statistical analysis, it is found that the satellite further away from the neutral sheet observed the high-speed flow earlier than the one close to the center. And the satellite further away from the neutral sheet observed higher X component of the plasma flow than the one close to the center.With the hypothesis that parallel flow keeps the same speed during its earthward propagation while central plasma sheet stream uniformly or suddenly brakes on its way to the earth, we calculated the position where the deceleration begins to be between 13Re and 17RE downtail, where the mid-earth reconnection site is supposed to occur.Then, we use the observation data from ARTEMIS and THEMIS to investigate the response of magnetosphere to the interplanetary shock wave. On 8 March 2012,we find that the ARTEMIS probes crossed the magnetopause many times within an hour in the region of X_gse=-60RE and Y_gse=0RE under northward IMF conditions after an oblique interplanetary shock impacted on the Earth. And the solar wind velocity vector in the shock downstream had been away from the Sun-Earth line,specially in Y direction. By the global MHD simulation, we reproduce the process of magnetopause crossings in X-Y plane by a virtual spacecraft under oblique shock conditions. It is found that the magnetopause is sharply deflected at the lunar distance. And these MHD results are qualitatively consistent with the observations.We change the normal of the shock to investigate the shock effect, and then produce a similar magnetotail distortion. Thus, we conclude that the shocked magnetotail at the lunar distance is mainly controlled by the solar wind with a timescale of about a quarter hour (the windsock effect). This result also lays the foundation of the magnetopause model which is expected to include the effect of the solar wind VY.We also present a study of the formation of the mixed plasma in the low latitude boundary layer region at the lunar distance for the northward IMF conditions that provides the evidence for the reconnection tailward and equatorward of the cusp region. The spin-resolution ion velocity distribution cuts taken by P1 show that some of the hot plasma with evident D-shape distribution may originate from the opened magnetic field by high latitude intermittent reconnection, and the others are caused by the Kelvin-Helmholtz instability.