Excitation and evolution of vertically polarised transverse loop oscillations by coronal rain
Excitation and evolution of vertically polarised transverse loop oscillations by coronal rain
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DOI：
10.1051/0004-6361/201730675
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发表时间：
2017-05
影响因子：
6.5
通讯作者：
E. Verwichte;P. Kohutova
中科院分区：
文献类型：
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作者：
E. Verwichte;P. Kohutova
上下文。日冕雨是由在日冕环中形成的冷的致密斑点组成的，是与热不稳定有关的灾难性冷却的一种表现。与日冕雨有关的振荡的性质和激发尚不清楚。目标。我们考虑日冕雨的观测，以阐明波的激发机制和演变特征。方法。我们分析了2014年8月17日一次振荡日冕雨事件的IRIS和Hinode/SOT观测数据，并使用经过试验和测试的时空分析技术确定了波浪特征作为时间的函数。结果。我们利用振荡的地震学能力，从振荡振幅推断出相对雨质量。这与振荡周期的演变是一致的，振荡周期显示环路在10-15分钟的时间内由于日冕雨的下降而失去了三分之一的质量。结论。我们提出了垂直极化横向环流振荡激发的第一个证据，该振荡是由环流顶部的灾难性冷却触发的，与由冷雨质量组成的环流质量的三分之二一致。
Context. Coronal rain is composed of cool dense blobs that form in solar coronal loops and are a manifestation of catastrophic cooling linked to thermal instability. The nature and excitation of oscillations associated with coronal rain is not well understood. Aims. We consider observations of coronal rain in a bid to elucidate the excitation mechanism and evolution of wave characteristics. Methods. We analyse IRIS and Hinode/SOT observations of an oscillating coronal rain event on 17 Aug 2014 and determine the wave characteristics as a function of time using tried and tested time-space analysis techniques. Results. We exploit the seismological capability of the oscillation to deduce the relative rain mass from the oscillation amplitude. This is consistent with the evolution of the oscillation period showing the loop loosing a third of its mass due to falling coronal rain in a 10-15 minute time period. Conclusions. We present first evidence of the excitation of vertically polarised transverse loop oscillations triggered by a catastrophic cooling at the loop top and consistent with two thirds of the loop mass comprising of cool rain mass.