摘要: The largest geomagnetic storms of solar cycle 24 so far occurred on 2015 March 17 and June 22 with D-st minima of -223 and -195 nT, respectively. Both of the geomagnetic storms show a multi-step development. We examine the plasma and magnetic field characteristics of the driving coronal mass ejections (CMEs) in connection with the development of the geomagnetic storms. A particular effort is to reconstruct the in situ structure using a Grad-Shafranov technique and compare the reconstruction results with solar observations, which gives a larger spatial perspective of the source conditions than one-dimensional in situ measurements. Key results are obtained concerning how the plasma and magnetic field characteristics of CMEs control the geomagnetic storm intensity and variability: (1) a sheath-ejecta-ejecta mechanism and a sheath-sheath-ejecta scenario are proposed for the multi-step development of the 2015 March 17 and June 22 geomagnetic storms, respectively;(2) two contrasting cases of how the CME flux-rope characteristics generate intense geomagnetic storms are found, which indicates that a southward flux-rope orientation is not a necessity for a strong geomagnetic storm;and (3) the unexpected 2015 March 17 intense geomagnetic storm resulted from the interaction between two successive CMEs plus the compression by a high-speed stream from behind, which is essentially the "perfect storm" scenario proposed by Liu et al. (i.e., a combination of circumstances results in an event of unusual magnitude), so the "perfect storm" scenario may not be as rare as the phrase implies.
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期刊:
ASTROPHYSICAL JOURNAL LETTERS
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分类:
地球科学
>>
空间物理学
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引用:
ChinaXiv:201605.01577
(或此版本
ChinaXiv:201605.01577V1)
DOI:10.12074/201605.01577V1
CSTR:32003.36.ChinaXiv.201605.01577.V1
- 推荐引用方式:
Liu, Ying D.,Hu, Huidong,Wang, Rui,Yang, Zhongwei,Zhu, Bei,Liu, Yi A.,Luhmann, Janet G.,Richardson, John D..(2016).PLASMA AND MAGNETIC FIELD CHARACTERISTICS OF SOLAR CORONAL MASS EJECTIONS IN RELATION TO GEOMAGNETIC STORM INTENSITY AND VARIABILITY.岩土力学预印本平台.[ChinaXiv:201605.01577]
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