1998年4—5月地球同步轨道MeV电子通量增强事件

MeV ELECTRON FLUX ENHANCEMENT EVENTS AT THE GEOSYNCHRONOUS ORBIT IN APRIL—MAY 1998

采用GOES 9卫星观测的能量大于 2MeV和大于 4MeV电子通量和行星际飞船ACE太阳风参数的高时间分辨率资料 ,以及磁暴指数Dst资料 ,分析了 1 998年 4— 5月期间地球同步轨道电子通量增强事件的时间和能量响应特征及其与行星际太阳风参数、磁暴和亚暴等扰动条件的对应关系 .结果表明 ,地球同步轨道相对论性 (MeV)电子通量增强事件有明显的周日变化 ,中午极大和午夜极小 .4月 2 2日和 5月 5日开始的两次大事件中 ,能量大于2MeV电子通量中午极大值上升到最大值的时间尺度分别约为 4天和 1天 ,中午极大值高于背景水平的持续时间分别为 1 3天 (4月 2 2日— 5月 4日 )和 1 6天 (5月 4日— 2 0日 )以上 .每次MeV电子通量增强事件的能量范围不完全相同 .两次大事件的上升段都对应于磁暴的恢复相 ,与太阳风动压脉冲、高速流脉冲和负Bz

The time and energy response characteristics of the relativistic (MeV) electron flux enhancement events at the geosynchronous orbit are analyzed and compared to the interplanetary disturbances and magnetic storms by using the high resolving data for the satellite GOES 9 electron fluxes and the spacecraft ACE solar wind parameters in April\_May 1998. The results show that there was the daily variation for the MeV electron flux at the geosynchronous orbit,the maximum flux at about the noon and minimum flux at about the midnight. In two great events starting at the geosynchronous orbit on April 22 and May 5,1998,the rising time scales of the noon maximum flux up to the peak fluxes for electrons of the energy >2MeV are for about 4 days and 1 day,respectively. The continued times of the noon maximum fluxes (greater than background level)are 13 days (from April 22 to May 4)and 16 days (from May 5 to 20),respectively. The energetic ranges for the MeV electron flux enhancement events are not same exactly. The rising phases for two great events in April\_May correspond to the recovery phases of storms and are closely associated with the solar wind dynamic pressure pulse,the high speed flow pulse,and the negative B z component of the interplanetary magnetic field (IMF).