Spatial and Temporal Scales of Coronal Magnetic Restructuring in the Development of Coronal Mass Ejections
Spatial and Temporal Scales of Coronal Magnetic Restructuring in the Development of Coronal Mass Ejections
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DOI：
10.1007/s11207-006-0181-7
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发表时间：
2006-12
期刊：
影响因子：
2.8
通讯作者：
Y. Wen;Jingxiu Wang;D. Maia;Yuzong Zhang;Hui Zhao;Guiping Zhou
中科院分区：
文献类型：
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作者：
Y. Wen;Jingxiu Wang;D. Maia;Yuzong Zhang;Hui Zhao;Guiping Zhou
日冕物质抛射（cme）是大规模日冕磁场重组或重新配置的结果。本文利用nanay radioheliography （NRH）图像和SOHO （Solar and heliosphere Observatory， SOHO）航天器上的实验，分析了四次CME事件，以了解导致CME起始的日冕重构。我们研究了射电发射的开始，持续时间和位置与EUV变暗和推断的CME开始有关。已经确定，早期日冕物质抛射在太阳盘上的发展是以一系列不同的射电暴为特征的。这些非热射电源与SOHO-EIT图像显示的日冕变暗同步出现，并且位于EUV变暗或正在变暗的区域内。确定了三个时间尺度：持续时间，单个射电暴的间隔时间，以及所有非热源的总体时间尺度。它们分别在大约几十秒到三分钟、一到三分钟和15到20分钟的范围内。单个射电发射似乎以日冕中快速磁声波的速度移动和膨胀；而非热射电辐射作为一个整体，似乎偶然地与连续的日冕重构相对应。如果我们用整个空间尺度除以所有射电暴的时间尺度来定义触发速度，则触发速度落在300 - 400 km s−1的范围内。这意味着日冕结构重组和重新配置的一般过程发生的速度比日冕的声速或声速慢。这是一种“拓扑波”的速度，即。时，连续拓扑从闭合场形态变为开场形态的速度。
It has been commonly accepted that coronal mass ejections (CMEs) result from the restructuring or reconfiguring of large-scale coronal magnetic fields. In this paper, we analyzed four CME events using Nançay Radioheliograph (NRH) images and the experiments onboard the Solar and Heliospheric Observatory (SOHO) spacecraft to understand the coronal restructuring leading to CME initiation. We investigated the onset, duration, and position of the radio emissions in relation to EUV dimming and the inferred CME onset.It has been identified that the early CME development on the solar disk is characterized by a series of distinct radio bursts. These nonthermal radio sources appeared in phase with coronal dimming shown by SOHO-EIT images and are located within the EUV dimming or ongoing dimming regions. Three time scales are identified: the duration, the separation of individual radio bursts, and the overall time scale of all of the nonthermal sources. They fall in the ranges of approximately tens of seconds to three minutes, one to three minutes, and 15 – 20 minutes, respectively. The individual radio emission seems to shift and expand at the speed of the fast magnetoacoustic waves in the corona; while the nonthermal radio emissions as a whole appear episodically to correspond to the successive coronal restructuring. If we define the triggering speed by dividing the overall spatial scale by the temporal scale of all the radio bursts, then the triggering speed falls in the range of 300 – 400 km s−1. This implies that the general process of coronal restructuring and reconfiguring takes place at a speed slower than either the Alvfenic or acoustic speed in the corona. This is a type of speed of “topology waves,”i.e., the speed of successive topology changes from closed to open field configuration.