Dependence of the large-scale, inner magnetospheric electric field on geomagnetic activity
Dependence of the large-scale, inner magnetospheric electric field on geomagnetic activity
复制标题
DOI：
10.1029/97ja03524
复制
发表时间：
1998-07
影响因子：
--
通讯作者：
D. Rowland;J. Wygant
中科院分区：
文献类型：
--
作者：
D. Rowland;J. Wygant
用加州大学伯克利分校/空军地球物理实验室的电场仪器对CRRES航天器进行了测量，以确定不同地磁活动水平的内磁层电场的平均结构。1991年1月至10月期间，在当地时间12：00至04：00地磁当地时间的当地时间段内，在L=2.5和L=8.5之间收集了数据。电场的平均黎明-黄昏分量几乎总是向黄昏的，随着Kp从0增加到9-，其幅度从0.05 mV/m缩放到1.5 mV/m。数据表明，电场被屏蔽出内磁层，屏蔽距离从大约L=5.0（Kp=1）开始，Kp每增加一个单位，向地球移动0.5 RE。有证据表明，当Kp ≥ 5时，电场穿透低于L=2.5。最有趣的方面，这项统计研究是发展中高Kp的区域之间的L=3.5和L=6的增强电场。在中等活动条件下，电场不会随着向地移动而单调减小。相反，它增加到一个广泛的局部最大值附近的位置，环电流通常被观察到是最强的，下降到该位置的接地。在该位置处的电场幅值可以是在较高L值处的2倍或更多倍。这些结果进行了讨论的背景下，大规模的流动和热等离子体的影响，内磁层。
Measurements made with the University of California, Berkeley/Air Force Geophysics Laboratory electric field instrument on the CRRES spacecraft are examined to determine the average structure of the inner magnetospheric electric field for different geomagnetic activity levels. Data were gathered between L=2.5 and L=8.5 over the period from January to October 1991 in the local time sector between 1200 and 0400 magnetic local time. The average dawn-dusk component of the electric field was nearly always duskward, scaling in magnitude from 0.05 mV/m to 1.5 mV/m as Kp increased from 0 to 9-. The data indicate that the electric field is shielded out of the inner magnetosphere, with the shielding distance starting at about L=5.0 for Kp=1 and moving 0.5 RE earthward for every unit increase in Kp. There is evidence that the electric field penetrates below L=2.5 for Kp ≥ 5. The most interesting aspect of this statistical study is the development for moderate to high Kp of a region of enhanced electric field between L=3.5 and L=6. For moderately active conditions the electric field does not decrease monotonically as one moves earthward. Instead, it increases to a broad local maximum near the position where the ring current is typically observed to be the strongest, falling off earthward of that position. The electric field magnitude can be a factor of 2 or more larger at this location than at higher L values. These results are discussed in the context of large-scale flows and the effects of hot plasma in the inner magnetosphere.