pulsations: A quasi-periodic field line oscillation in the magnetosphere
pulsations: A quasi-periodic field line oscillation in the magnetosphere
复制标题
脉动：磁层中的准周期磁力线振荡
DOI：
10.1029/96ja00361
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发表时间：
1996
影响因子：
2.4
通讯作者：
O. Watanabe
中科院分区：
文献类型：
--
作者：
O. Saka;H. Akaki;O. Watanabe
研究了倾角赤道和地球同步高度(GO5和6颗卫星)的磁力计数据和地球同步轨道航天器(1982-019,1984-037,1984-129)的高能粒子数据，以研究与地面PI2起始有关的场线和粒子特征。在地面站观测到的PI2脉动被讨论为与亚暴开始时的场重新配置有关的在磁层午夜扇区发射的场扰动。在地球同步轨道上，伴随着地面PI 2脉动的开始，在夜侧区域经常观察到准周期场线振荡和粒子注入。在本报告所选的216个Pi2事件中，16%的事件表现出准周期场线振荡。空间振荡的主导周期类似于但不等于相应的地面PI 2脉动的主导周期。空间中的振荡主要在方位方向上极化，直流偏移量发展成场对齐电流信号，即在午夜前(午夜后)扇区向东(向西)。通过在赤道午夜扇区加入等离子体压力的突然增加，模拟了强迫场线振荡，预计这是亚暴扩张开始时粒子注入的结果。参考模型计算的结果，我们讨论了准周期振荡与地球同步轨道上的等离子体注入的相关性。
Magnetometer data at dip-equator and at geosynchronous altitudes (GOES 5 and 6 satellites) and energetic particle data from geosynchronous spacecraft (1982-019, 1984-037, 1984-129) are studied to investigate field line and particle signatures associated with ground Pi 2 onset. Pi 2 pulsations observed at the ground station are discussed as field disturbances that axe launched in the midnight sector of the magnetosphere in association with field reconfiguration at substorm onset. In the geosynchronous orbit, both quasi-periodic field line oscillations and particle injections are often observed in the nightside sector in association with the onset of ground Pi 2 pulsations. Of 216 Pi 2 events selected in this report, 16% showed associated quasi-periodic field line oscillations. The dominant periods of the oscillations in space are similar to but not equal to those of the corresponding ground Pi 2 pulsations. The oscillations in space are polarized primarily in the azimuthal direction with a dc offset that develops to form a field-aligned current signature, namely, eastward (westward) directed in the premidnight (postmidnight) sector. Simulation of forced field line oscillations has been carried out by adding the sudden increase in plasma pressure in the equatorial midnight sector region that is expected to come from particle injection at substorm expansion onset. We discuss the relevance of the quasi-periodic oscillations to plasma injections at geosynchronous altitudes with reference to the result of the model calculations.