上游太阳风中高能电子向同步轨道区的传输

通常认为，同步轨道区的电子通量增加是由于磁暴或者上游太阳风高速流的扰动所引起．近来的观测表明，起源于太阳活动的行星际高能电子也是引起同步轨道电子通量增加的重要原因之一．Zhao等在研究2000年7月14日太阳剧烈活动时发现，同步轨道区相对论电子通量巨幅增加时没有观察到上游太阳风高速流的扰动，并且磁暴发生在电子通量事件之后．采用解析磁场模型和实际磁场模型(T96模型)模拟来自太阳的相对论电子在磁尾中的运动特性．计算结果表明，当行星际磁场南向时，进入到磁尾的行星际相对论电子可以从较远的磁尾区域运动到同步轨道区域．这一研究结果从理论上论证了起源于太阳活动的高能电子可以对同步轨道区相对论电子通量的增加产生重要的作用．

TRANSPORT OF RELATIVISTIC ELECTRONS FROM UPSTREAM SOLAR WIND INTO GEO-SYNCHRONOUS ORBIT

A new mechanism is brought forward to explain the tremendous relativistic electron flux enhancement events at the geo-synchronous orbit. There have been two explanations advanced before. The first theory says that the magnetic storms cause the relativistic electron flux enhancement events; according to the second one, it is the disturbance of the higher velocity branch of the solar wind that results in the events. However, in the events starting on July 14, 2000, which were studied, there had no evident disturbance of the velocity of the solar wind and the magnetic storms lagged behind the relativistic electron flux enhancement. In the present paper, we separately simulate the motions of the relativistic electrons in the x-dependent Harris-like equilibrium model and a more realistic magnetic model-T96 Model of Tsyganenko. According to the results of numerical simulation, we suggest that: when the IMF directed southward, the magnetic re-connection occurred at the dayside magnetopause. Therefore, the relativistic electrons can move to the magnetotail from the dayside magnetopause, then the electrons reached the geosynchronous orbit from the tail region by stochastic motion in the current sheet.