The State of the Heliosphere Revealed by Limb-halo Coronal Mass Ejections in Solar Cycles 23 and 24
The State of the Heliosphere Revealed by Limb-halo Coronal Mass Ejections in Solar Cycles 23 and 24
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第 23 和 24 太阳周期中的临晕日冕物质抛射揭示的日光层状态
DOI：
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发表时间：
2020
影响因子：
4.9
通讯作者：
S. Yashiro
中科院分区：
文献类型：
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作者：
N. Gopalswamy;S. Akiyama;S. Yashiro
我们比较了太阳活动周23和24期间起源于边缘附近（中央子午线距离范围为60°-190 °）的晕日冕物质抛射（CME）的性质，以量化日光层状态对CME性质的影响。在第23和24周期中分别有44和38个肢体晕。以太阳黑子数的平均值来标准化，在第24周有42%的边缘晕。虽然临晕作为一个整体非常快（平均速度为1464 km s−1），但第24周的临晕比第23周的临晕慢了26%。我们引入了一个新的参数，日心距离的CME前缘时，CME成为一个完整的晕;这个高度是显着较短的周期24（由20%），并有一个较低的截止在206 Rs。这些结果表明，第24周CME比第23周CME更快、更慢地形成晕。另一方面，耀斑的大小是非常相似的，在两个周期，排除了可能的喷发特征，有助于不同的CME属性。总之，这项研究揭示了日球层总压降低的影响，这使得第24周期的CME比第23周期更快地膨胀并成为晕。我们的研究结果具有重要意义的CME在周期25（预计类似于周期24）的空间天气后果，并了解晕计数的差异报告的自动和手动目录。
We compare the properties of halo coronal mass ejections (CMEs) that originate close to the limb (within a central meridian distance range of 60°–∼90°) during solar cycles 23 and 24 to quantify the effect of the heliospheric state on CME properties. There are 44 and 38 limb halos in cycles 23 and 24, respectively. Normalized to the cycle-averaged total sunspot number, there are 42% more limb halos in cycle 24. Although the limb halos as a population are very fast (average speed ∼1464 km s−1), cycle-24 halos are slower by ∼26% than the cycle-23 halos. We introduce a new parameter, the heliocentric distance of the CME leading edge at the time a CME becomes a full halo; this height is significantly shorter in cycle 24 (by ∼20%) and has a lower cutoff at ∼6 Rs. These results show that cycle-24 CMEs become halos sooner and at a lower speed than the cycle-23 ones. On the other hand, the flare sizes are very similar in the two cycles, ruling out the possibility of eruption characteristics contributing to the differing CME properties. In summary, this study reveals the effect of the reduced total pressure in the heliosphere that allows cycle-24 CMEs to expand more and become halos sooner than in cycle 23. Our findings have important implications for the space-weather consequences of CMEs in cycle 25 (predicted to be similar to cycle 24) and for understanding the disparity in halo counts reported by automatic and manual catalogs.