A CORONAL SEISMOLOGICAL STUDY WITH STREAMER WAVES
A CORONAL SEISMOLOGICAL STUDY WITH STREAMER WAVES
复制标题
流光波的日冕地震学研究
DOI：
10.1088/0004-637x/728/2/147
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发表时间：
2011-02-20
影响因子：
4.9
通讯作者：
Li, Xing
中科院分区：
文献类型：
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作者：
Chen, Y.;Feng, S. W.;Li, Xing
我们提出了一种新的方法来计算阿尔芬速度和磁场强度沿流光等离子体片在外冕。该方法基于最近对流光波的观测，流光波被认为是等离子体片结构携带的快速扭结体模，它是在快速日冕物质抛射(CME)对附近流光的影响下产生的。该模式以由两个分量组成的相速度向外传播。一个是模式在等离子体静止坐标系中的相速度，另一个是太阳风沿等离子体片流动的速度。根据简化的磁化等离子体平板模型的线性波色散分析，前者可以很好地用等离子体片外的Alfven速度来表示。阿尔芬速度的径向分布可以在对太阳风的速度施加约束的情况下推导出来，这是通过测量在风中被动流动的流光斑点来完成的。一旦指定了电子密度分布，就可以通过对观测到的极化亮度数据进行倒置来描绘日冕磁场强度的径向分布。比较第一个波谷和第二个波峰对应的诊断结果，我们发现Alfven速度和固定距离处的磁场强度都随着时间的推移而下降。这暗示了日冕运动扰动的日冕的恢复过程。
We present a novel method to evaluate the Alfven speed and the magnetic field strength along the streamer plasma sheet in the outer corona. The method is based on recent observations of streamer waves, which are regarded as the fast kink body mode carried by the plasma sheet structure and generated upon the impact of a fast coronal mass ejection (CME) on a nearby streamer. The mode propagates outward with a phase speed consisting of two components. One is the phase speed of the mode in the plasma rest frame and the other is the speed of the solar wind streaming along the plasma sheet. The former can be well represented by the Alfven speed outside the plasma sheet, according to a linear wave dispersion analysis with a simplified slab model of magnetized plasmas. The radial profiles of the Alfven speed can be deduced with constraints put on the speed of the solar wind, which is done by making use of the measurements of streamer blobs flowing passively in the wind. The radial profiles of the strength of the coronal magnetic field can be depicted once the electron density distribution is specified, this is done by inverting the observed polarized brightness data. Comparing the diagnostic results corresponding to the first wave trough and the following crest, we find that both the Alfven speed and magnetic field strength at a fixed distance decline with time. This is suggestive of the recovering process of the CME-disturbed corona.