Storm time observations of electromagnetic ion cyclotron waves at geosynchronous orbit: GOES results
Storm time observations of electromagnetic ion cyclotron waves at geosynchronous orbit: GOES results
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DOI：
10.1029/2009ja014516
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发表时间：
2010-05-15
影响因子：
2.8
通讯作者：
Thomsen, M. F.
中科院分区：
文献类型：
--
作者：
Fraser, B. J.;Grew, R. S.;Thomsen, M. F.
电磁离子回旋（EMIC）波可能有助于环电流离子和辐射带电子损失，理论研究表明，这些过程可能是最有效的地磁风暴的主相。然而，在恢复阶段，更频繁地观察到EMIC波的地基签名，Pc 1-Pc 2地磁脉动。通过对1996-2003年22个Dst < -30 nT的磁暴的个例和统计研究，探讨了EMIC波与不同磁暴相的关系。GOES 8号、9号和10号地球同步卫星磁强计的高分辨率数据提供了关于风暴开始（定义为Dst负偏移的开始）+/-3天内0-1 Hz波段EMIC波活动的信息。22个风暴中有13个在主相期间出现EMIC波。在对两个风暴的案例研究中，在一个风暴的主阶段和另一个风暴的恢复阶段，可以看到波浪的强度较高。在风暴前、风暴和早期恢复阶段，高达500 nT（2）Hz（-1）的功率谱密度是相似的。对22个风暴的叠加历元分析表明，主位相期间78%的波事件发生在He+带。风暴开始后，主要阶段仅占总体事件的29%，而恢复阶段则占71%，长达3天。发现风暴之间的一些差异取决于太阳风驱动器。等离子体羽流或膨胀的等离子体云可能有助于增强地球同步轨道上的EMIC波活动。
Electromagnetic ion cyclotron (EMIC) waves may contribute to ring current ion and radiation belt electron losses, and theoretical studies suggest these processes may be most effective during the main phase of geomagnetic storms. However, ground-based signatures of EMIC waves, Pc1-Pc2 geomagnetic pulsations, are observed more frequently during the recovery phase. We investigate the association of EMIC waves with various storm phases in case and statistical studies of 22 geomagnetic storms over 1996-2003, with an associated Dst < -30 nT. High-resolution data from the GOES 8, 9, and 10 geosynchronous satellite magnetometers provide information on EMIC wave activity in the 0-1 Hz band over +/-3 days with respect to storm onset, defined as commencement of the negative excursion of Dst. Thirteen of 22 storms showed EMIC waves occurring during the main phase. In case studies of two storms, waves were seen with higher intensity in the main phase in one and the recovery phase in the other. Power spectral densities up to 500 nT(2) Hz(-1) were similar in prestorm, storm, and early recovery phases. Superposed epoch analysis of the 22 storms shows 78% of wave events during the main phase occurred in the He+ band. After storm onset the main phase contributed only 29% of events overall compared to 71% during recovery phase, up to 3 days. Some differences between storms were found to be dependent on the solar wind driver. Plasma plumes or an inflated plasmasphere may contribute to enhancing EMIC wave activity at geosynchronous orbit.