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arXiv 2212.00510astro-ph.SRastro-ph.EP
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空间时代的磁暴：发生和与变化的太阳活动的关系

Magnetic storms during the space age: Occurrence and relation to varying solar activity

Kalevi Mursula, Timo Qvick, Lauri Holappa, Timo Asikainen

发表信息：
J. Geophys. Res.: Space, 127, e2022JA030830
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摘要：

本文用Dst和Dxt指数研究了空间年龄（1957-2021）磁暴的发生。我们发现2526/2743磁暴的Dxt/Dst指数，其中45%的弱，40%的中等，12%的强烈和3%的大风暴。空间时代风暴的发生是伴随着太阳黑子活动的缓慢减少和太阳磁结构的相关变化。我们量化了太阳黑子与日冕物质抛射风暴在空间年龄的五个周期中的关系.我们解释了不同的太阳活动如何改变日光层电流片（HCS）的结构，以及这如何影响HSS/CIR风暴。太空时代始于1957年至1960年的创纪录风暴数量，大约每周一次风暴。太阳极场在第22周达到极大值，导致了异常薄的HCS，并在20世纪90年代出现了大型HSS/CIR风暴的空间年龄记录。在第23个太阳活动周期的最低点，CME风暴的发生率降低到太阳黑子预测的水平以下，这是太空时代唯一的一次。自第23周以来，弱的太阳黑子活动削弱了太阳极场，扩大了HCS，这减少了大型和中型HSS/CIR风暴的发生。由于HCS很宽，自第23周以来，地球有50%的时间处于缓慢的太阳风中。宽的HCS也使大、中等的HSS/CIR风暴出现在最近几个周期的早期下降阶段，而在较活跃的20-22周期中，它们出现在晚期下降阶段。

英文摘要：

We study the occurrence of magnetic storms in space age (1957-2021) using Dst and Dxt indices. We find 2526/2743 magnetic storms in the Dxt/Dst index, out of which 45% are weak, 40% moderate, 12% intense and 3% major storms. Occurrence of storms in space age follows the slow decrease of sunspot activity and the related change in solar magnetic structure. We quantify the sunspot - CME storm relation in the five cycles of space age. We explain how the varying solar activity changes the structure of the heliospheric current sheet (HCS), and how this affects the HSS/CIR storms. Space age started with a record number of storms in 1957-1960, with roughly one storm per week. Solar polar fields attained their maximum in cycle 22, which led to an exceptionally thin HCS, and a space age record of large HSS/CIR storms in 1990s. In the minimum of cycle 23, for the only time in space age, CME storm occurrence reduced below that predicted by sunspots. Weak sunspot activity since cycle 23 has weakened solar polar fields and widened the HCS, which has decreased the occurrence of large and moderate HSS/CIR storms. Because of a wide HCS, the Earth has spent 50% of its time in slow solar wind since cycle 23. The wide HCS has also made large and moderate HSS/CIR storms occur in the early declining phase in recent cycles, while in the more active cycles 20-22 they occurred in the late declining phase.

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