Evolution of Coronal Holes and Implications for High-Speed Solar Wind During the Minimum Between Cycles 23 and 24
Evolution of Coronal Holes and Implications for High-Speed Solar Wind During the Minimum Between Cycles 23 and 24
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DOI：
10.1007/s11207-010-9677-2
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发表时间：
2011-12-01
期刊：
影响因子：
2.8
通讯作者：
de Toma, G.
中科院分区：
文献类型：
--
作者：
de Toma, G.
我们分析了第 23 至 24 个周期之间延长的最小值期间太阳上出现的日冕洞，研究它们的演化，检查地球附近太阳风速的影响，并将其与 1996 年之前的最小值进行比较。我们结合 SOHO/EIT 和 STEREO/EUVI 的 EUV 观测以及磁图来识别日冕洞并确定其大小和位置。我们发现，2006年至2009年太阳活动长期低迷的特点是极地磁场较弱，极地日冕洞比之前观测到的极小期要小。我们还发现，直到 2008 年，太阳上一直存在大型低纬度日冕洞，并且仍然是周期性高速太阳风流的重要来源。到2008年底，这些低纬度日冕洞开始关闭，并最终于2009年消失，而在第24周期活动区的残余物中形成了更小的中纬度日冕洞，将地球上的太阳风来源转移到了更高纬度。
We analyze coronal holes present on the Sun during the extended minimum between Cycles 23 and 24, study their evolution, examine the consequences for the solar wind speed near the Earth, and compare it with the previous minimum in 1996. We identify coronal holes and determine their size and location using a combination of EUV observations from SOHO/EIT and STEREO/EUVI and magnetograms. We find that the long period of low solar activity from 2006 to 2009 was characterized by weak polar magnetic fields and polar coronal holes smaller than observed during the previous minimum. We also find that large, low-latitude coronal holes were present on the Sun until 2008 and remained important sources of recurrent high-speed solar wind streams. By the end of 2008, these low-latitude coronal holes started to close down, and finally disappeared in 2009, while smaller, mid-latitude coronal holes formed in the remnants of Cycle 24 active regions shifting the sources of the solar wind at the Earth to higher latitudes.