High-beta plasma blobs in the morningside plasma sheet
High-beta plasma blobs in the morningside plasma sheet
复制标题
DOI：
10.1007/s00585-999-1592-1
复制
发表时间：
1999-12
影响因子：
1.9
通讯作者：
G. Haerendel;Wolfgang Baumjohann;E. Georgescu;R. Nakamura;L. Kistler;B. Klecker;H. Kucharek;A. Vaivads;T. Mukai;S. Kokubun
中科院分区：
文献类型：
--
作者：
G. Haerendel;Wolfgang Baumjohann;E. Georgescu;R. Nakamura;L. Kistler;B. Klecker;H. Kucharek;A. Vaivads;T. Mukai;S. Kokubun
赤道-S经常遇到，即在1998年3月1日至4月17日之间的30%的轨道上，在深夜/清晨，在大约9 RE之外，磁场强度通常持续5-15分钟的强烈变化。发现血浆β值非常高，在1和10或更高之间变化。赤道-S和Geotail之间的紧密结合揭示了这些“等离子体斑点”的空间结构和它们的寿命。它们通常在经度上宽5-10°，相对于赤道具有反对称的等离子体或磁压分布，同时是低纬度现象（<15°）。它们缓慢地向太阳漂移，穿过赤道交换等离子体，寿命至少为15-30分钟。虽然它们的空间结构可能是由于某种镜像不稳定性，但人们对高β等离子体的起源知之甚少。据推测，晨边边界层有点进一步尾部可能是这种等离子体的来源。这与等离子体团在安静条件下发生的偏好是一致的，尽管它们也在亚暴期间被发现。晨边椭圆区的极光现象与此的关系尚不确定。能量沉积可能大多太弱而不能产生可见的签名。然而，斑片状极光仍然是一个候选人更不安的时期。
Equator-S frequently encountered, i.e. on 30%0of the orbits between 1 March and 17 April 1998, strong variations of the magnetic field strength of typically 5–15-min duration outside about 9REduring the late-night/early-morning hours. Very high-plasma beta values were found, varying between 1 and 10 or more. Close conjunctions between Equator-S and Geotail revealed the spatial structure of these “plasma blobs” and their lifetime. They are typically 5–10° wide in longitude and have an antisymmetric plasma or magnetic pressure distribution with respect to the equator, while being altogether low-latitude phenomena (<15°). They drift slowly sunward, exchange plasma across the equator and have a lifetime of at least 15–30 min. While their spatial structure may be due to some sort of mirror instability, little is known about the origin of the high-beta plasma. It is speculated that the morningside boundary layer somewhat further tailward may be the source of this plasma. This would be consistent with the preference of the plasma blobs to occur during quiet conditions, although they are also found during substorm periods. The relation to auroral phenomena in the morningside oval is uncertain. The energy deposition may be mostly too weak to generate a visible signature. However, patchy aurora remains a candidate for more disturbed periods.