气候变化领域集成服务门户(CCPortal): Using the aa Index Over the Last 14 Solar Cycles to Characterize Extreme Geomagnetic Activity

CCPortal

DOI	10.1029/2019GL086524
	Using the aa Index Over the Last 14 Solar Cycles to Characterize Extreme Geomagnetic Activity
	Chapman S.C.; Horne R.B.; Watkins N.W.
发表日期	2020
ISSN	0094-8276
卷号	47 期号:3
英文摘要	Geomagnetic indices are routinely used to characterize space weather event intensity. The DST index is well resolved but is only available over five solar cycles. The aa index extends over 14 cycles but is highly discretized with poorly resolved extremes. We parameterize extreme aa activity by the annual-averaged top few percent of observed values, show that these are exponentially distributed, and they track annual DST index minima. This gives a 14-cycle average of ∼4% chance of at least one great (DST < −500 nT) storm and ∼28% chance of at least one severe (DST < −250 nT) storm per year. At least one DST = −809 [−663,−955] nT event in a given year would be a 1:151 year event. Carrington event estimate DST ∼ −850 nT is within the same distribution as other extreme activity seen in aa since 1868 so that its likelihood can be deduced from that of more moderate events. Events with DST ≲ −1,000 nT are in a distinct class, requiring special conditions. ©2020. The Authors.
英文关键词	Storms; aa index; Carrington event; Geomagnetic activities; Geomagnetic indices; Geomagnetic storm; Observed values; Solar cycle; Space weather; Geomagnetism; extreme event; geomagnetic storm; index method; solar cycle; weather; Carrington; North Dakota; United States
语种	英语
来源期刊	Geophysical Research Letters
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/170788
作者单位	Centre for Fusion, Space and Astrophysics, Physics Department, University of Warwick, Coventry, United Kingdom; British Antarctic Survey, Cambridge, United Kingdom; Centre for the Analysis of Time Series, London School of Economics and Political Science, London, United Kingdom; Faculty of Science, Technology, Engineering and Mathematics, Open University, Milton Keynes, United Kingdom
推荐引用方式 GB/T 7714	Chapman S.C.,Horne R.B.,Watkins N.W.. Using the aa Index Over the Last 14 Solar Cycles to Characterize Extreme Geomagnetic Activity[J],2020,47(3).
APA	Chapman S.C.,Horne R.B.,&Watkins N.W..(2020).Using the aa Index Over the Last 14 Solar Cycles to Characterize Extreme Geomagnetic Activity.Geophysical Research Letters,47(3).
MLA	Chapman S.C.,et al."Using the aa Index Over the Last 14 Solar Cycles to Characterize Extreme Geomagnetic Activity".Geophysical Research Letters 47.3(2020).