Geomagnetic activity associated with earth passage of interplanetary shock disturbances and coronal mass ejections
Geomagnetic activity associated with earth passage of interplanetary shock disturbances and coronal mass ejections
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DOI：
10.1029/91ja00316
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发表时间：
1991-05
影响因子：
--
通讯作者：
J. Gosling;D. McComas;J. Phillips;S. Bame
中科院分区：
文献类型：
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作者：
J. Gosling;D. McComas;J. Phillips;S. Bame
日冕物质抛射事件（CMEs）是1au太阳风中重要的等离子体和磁场偶然来源，约占最后一次太阳活动极大期黄道面所有太阳风测量值的10%。先前的研究表明，几乎所有太阳风中的瞬态激波扰动都是由快速日冕物质抛射引起的。利用最近认识到的以逆流太阳风电子事件的形式在太阳风数据中区分cme的能力，本文探讨了激波干扰和cme在刺激地磁活动方面的总体有效性。研究范围限定在1978年8月中旬至1982年10月中旬，跨越了最后一次太阳活动高峰，当时ISEE 3在距离地球上游220 Re的L1拉格朗日点附近的轨道上运行。我们发现，在那个时代的37个最大的地磁风暴中，除了一个之外，所有的都与地球的日冕物质抛射和/或激波干扰有关，这些风暴中的绝大多数（37个中的27个）与行星际事件有关，在这些事件中，地球遇到了激波和驱动激波的日冕物质抛射（激波/日冕物质抛射事件）。虽然日冕物质抛射和（或）冲击扰动随着地磁活动水平的增加而日益成为地磁活动的原因，但许多较小的地磁扰动与这些事件无关。此外，根据行星地磁指数Kp测量，大约一半的日冕物质抛射和地球遇到的一半冲击干扰没有产生任何实质性的地磁活动。地球指向的cme和激波扰动的地磁有效性与流速、磁场强度和与事件相关的南向场分量的强度直接相关。靠近太阳的日冕物质抛射的初始速度似乎是决定一个指向地球的事件是否会有效地激发大规模地磁扰动的最关键因素。
Coronal mass ejection events (CMEs) are important occasional sources of plasma and magnetic field in the solar wind at 1 AU, accounting for approximately 10% of all solar wind measurements in the ecliptic plane during the last solar activity maximum. Previous work indicates that virtually all transient shock wave disturbances in the solar wind are driven by fast CMEs. Using a recently appreciated capability for distinguishing CMEs in solar wind data in the form of counterstreaming solar wind electron events, this paper explores the overall effectiveness of shock wave disturbances and CMEs in general in stimulating geomagnetic activity. The study is confined to the interval from mid-August 1978 through mid-October 1982, spanning the last solar activity maximum, when ISEE 3 was in orbit about the L1 Lagrange point 220 Re upstream from Earth. We find that all but one of the 37 largest geomagnetic storms in that era were associated with Earth passage of CMEs and/or shock disturbances, with the large majority of these storms (27 out of 37) being associated with interplanetary events where Earth encountered both a shock and the CME driving the shock (shock/CME events). Although CMEs and/or shock disturbances were increasingly the cause of geomagnetic activity as the level of geomagnetic activity increased, many smaller geomagnetic disturbances were unrelated to these events. Further, approximately half of all CMEs and half of all shock disturbances encountered by Earth did not produce any substantial geomagnetic activity as measured by the planetary geomagnetic index Kp. The geomagnetic effectiveness of Earth directed CMEs and shock wave disturbances was directly related to the flow speed, the magnetic field magnitude, and the strength of the southward (GSM) field component associated with the events. The initial speed of a CME close to the Sun appears to be the most crucial factor in determining if an earthward directed event will be effective in exciting a large geomagnetic disturbance.