Magnetohydrodynamic Seismology of Quiet Solar Active Regions
Magnetohydrodynamic Seismology of Quiet Solar Active Regions
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DOI：
10.3847/2041-8213/ab4792
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发表时间：
2019-10-20
影响因子：
7.9
通讯作者：
Nakariakov, V. M.
中科院分区：
文献类型：
--
作者：
Anfinogentov, Sergey A.;Nakariakov, V. M.
最近发现的普遍存在的等离子环的低振幅无衰减扭结振荡使得对日冕进行定期的地震学探测成为可能。特别是，与基于耀斑和火山喷发激发的大振幅衰减扭结振荡的传统应用地震学相比，无衰减振荡可以潜在地为预测提供必要的诊断。我们分析了2010年7月10日活跃区域NOAA 12107在安静时期的几个不同环路的无衰减扭结振荡，当时太阳动力学观测台上的大气成像组件在极紫外波段观测到它的西翼。利用运动放大技术估计了振荡周期。振荡回路的长度是通过测量其脚点的位置在其半圆形的假设内确定的。考虑到背景等离子体的未知空间尺度，根据观测到的强度对比估计了环路中的密度对比。这些测量的结合使我们能够确定活跃区域扭结和阿尔芬速度的分布。因此，我们证明了在平静时期获得日冕活动区地震信息的可能性。
The ubiquity of recently discovered low-amplitude decayless kink oscillations of plasma loops allows for the seismological probing of the corona on a regular basis. In particular, in contrast to traditionally applied seismology that is based on the large-amplitude decaying kink oscillations excited by flares and eruptions, decayless oscillations can potentially provide the diagnostics necessary for their forecasting. We analyzed decayless kink oscillations in several distinct loops belonging to active region NOAA 12107 on 2010 July 10 during its quiet time period, when it was observed on the west limb in extreme ultraviolet by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. The oscillation periods were estimated with the use of the motion magnification technique. The lengths of the oscillating loops were determined within the assumption of its semicircular shape by measuring the position of their footpoints. The density contrast in the loops was estimated from the observed intensity contrast accounting for the unknown spatial scale of the background plasma. The combination of those measurements allows us to determine the distribution of kink and Alfven speeds in the active region. Thus, we demonstrate the possibility of obtaining seismological information about coronal active regions during the quiet periods of time.