Particle acceleration in the magnetotail associated with magnetospheric substorms and storms

1. 基于GEOTAIL磁场和等离子体数据的统计研究，讨论了与亚暴相关的彗尾快速流动的径向演化。尾流有系统的尾流和空间演化，可以识别出典型的20-30分钟的时间尺度，而向地流则因事件而异。利用GEOTAIL获得的等离子体和磁场数据，研究了与地磁风暴相关的远尾结构的变化。当卫星位于X=- 83r_e和*=-210R_E之间的远尾时，研究了1993年10月至1994年10月间的13次风暴间隔。GEOTAIL观测了所有风暴期间的磁鞘，包括卫星位于名义尾轴附近的风暴。研究发现，在风暴主阶段，远尾也储存了-5 × 10^<15>J的平均能量，这与以往研究中报道的强次风暴生长阶段中尾储存的能量相当。利用SAMPEX卫星资料研究了地磁暴主期和恢复初期外辐射带电子通量的变化。我们研究了25个具有不同活动水平的明确风暴。通过与简单的环电流磁场扰动模型的比较，表明其减小是由于环电流粒子对风暴时间磁场的绝热减速响应。这种绝热响应在L=4-5之间最为明显，在1 MeV辐射带的中心，环电流引起的磁扰动可能产生最大的影响。

1. We discuss the radial evolution of the fast flow in the tail associated with substorm based on statistical studies using GEOTAIL magnetic field and plasma data. While the tailward flow has a systematic tailward and spatial evolution, where a typical timescale 20-30 minutes can be identified, the earthward flow is differs from event to event.2. Changes in the structure of the distant tail associated with geomagnetic storms are studied by using plasma and magnetic field data obtained from GEOTAIL.Thirteen storm intervals between October 1993 and October 1994 are examined when the satellite was located in the distant tail between X=-83R_Eand*=-210R_E. GEOTAIL observed the magnetosheath during all storms including those when the satellite was located near the nomianl tail axis. It is found that an average energy of -5x 10^<15>J is stored also in the distant tail during the storm main phase, which is a comparable value to that stored in the midtail during an intense substorm growth phase reported in the previous studies.3. We studied flux variations in the outer radiation belt electrons during main phase and early recovery phase of geomagnetic storm using data obtained by SAMPEX.We examined 25 well defined storms with different activity level. By comparing with a simple model of ring current magnetic field perturbations, it is shown that the decrease is attributed to the adiabatic deceleration in response to the storm time magnetic field due to ring current particle. Such adiabatic response in most clearly detected between L=4-5, at the center of the 1 MeV radiation belt, and where the magnetic perturbation due to the ring current could have largest effect.