arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2210.14535astro-ph.SR
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第23和24太阳活动周期间近地行星际日冕物质抛射及其与DH型II射电爆发的联系

Near-Earth Interplanetary Coronal Mass Ejections and Their Association with DH Type II Radio Bursts During Solar Cycles 23 and 24

Binal D. Patel, Bhuwan Joshi, Kyung-Suk Cho, Rok-Soon Kim, Yong-Jae Moon

摘要:

分析了第23周和第24周行星际日冕物质抛射的特征。本分析主要基于近地ICME目录(Richardson和Cane,2010年)。这项研究的一个重要方面是了解近地和地球有效方面的ICME的关联(II型ICME)与缺乏(非II型ICME)的十米-百米(DH)II型无线电爆发,检测风/波和STEREOS/波。值得注意的是,由CME驱动的DH II型射电爆发表明强大的MHD冲击离开内日冕并进入行星际介质。我们发现,与前一个周期相比,太阳周期24中ICME的发生率大幅减少了56%(64对147事件)。有趣的是,尽管ICME/CME计数显著降低,但两个周期包含几乎相同的II型ICME分数(约47%)。我们的分析表明,即使在1 AU的大距离上,II型CME也保持着比非II型事件更高的速度(523 km/s对440 km/s)。虽然有一个明显的趋势,随着CME初始速度的增加,ICME渡越时间的减少,也存在一个明显的宽范围内的CME速度。从上下文来看,第23周期展示了10个过境时间较短的事件,主要是II类事件,过境时间在20-40小时之间,而有趣的是,第24周期几乎完全没有这种“快速”事件。我们发现一个显着减少的参数$V_{ICME} \times B_{z}$,黎明到黄昏的电场,由39%,在太阳活动周期24与前一个周期相比。此外,$V_{ICME} \times B_{z}$显示出与Dst指数的强相关性,这甚至超过了单独考虑$B_{z}$和$V_{ICME}$。上述结果暗示了$V_{ICME} \times B_{z}$在有效调节ICME的地球有效性方面的关键作用。

英文摘要:

We analyse the characteristics of interplanetary coronal mass ejections (ICMEs) during Solar Cycles 23 and 24. The present analysis is primarily based on the near-Earth ICME catalogue (Richardson and Cane, 2010). An important aspect of this study is to understand the near-Earth and geoeffective aspects of ICMEs in terms of their association (type II ICMEs) versus absence (non-type II ICMEs) of decameter-hectometer (DH) type II radio bursts, detected by Wind/WAVES and STEREOS/WAVES. Notably, DH type II radio bursts driven by a CME indicate powerful MHD shocks leaving the inner corona and entering the interplanetary medium. We find a drastic reduction in the occurrence of ICMEs by 56% in Solar Cycle 24 compared to the previous cycle (64 versus 147 events). Interestingly, despite a significant decrease in ICME/CME counts, both cycles contain almost the same fraction of type II ICMEs (~47%). Our analysis reveals that, even at a large distance of 1 AU, type II CMEs maintain significantly higher speeds compared to non-type II events (523 km/s versus 440 km/s). While there is an obvious trend of decrease in ICME transit times with increase in the CME initial speed, there also exists a noticeable wide range of transit times for a given CME speed. Contextually, Cycle 23 exhibits 10 events with shorter transit times ranging between 20-40 hours of predominantly type II categories while, interestingly, Cycle 24 almost completely lacks such "fast" events. We find a significant reduction in the parameter $V_{ICME} \times B_{z}$, the dawn to dusk electric field, by 39% during Solar Cycle 24 in comparison with the previous cycle. Further, $V_{ICME} \times B_{z}$ shows a strong correlation with Dst index, which even surpasses the consideration of $B_{z}$ and $V_{ICME}$ alone. The above results imply the crucial role of $V_{ICME} \times B_{z}$ toward effectively modulating the geoeffectiveness of ICMEs.

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