Intensity and velocity oscillations in a flaring active region
Intensity and velocity oscillations in a flaring active region
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耀斑活动区域的强度和速度振荡
DOI：
10.1093/mnras/stad3386
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发表时间：
2024
影响因子：
4.8
通讯作者：
Millar D
中科院分区：
文献类型：
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作者：
Millar D
色球振荡可以让我们了解太阳大气中的物理环境，无论是在安静的太阳和耀斑条件。许多作者报告说，3分钟振荡的普遍性增加，这被认为是由影响色球层的事件（如耀斑）激发的。在这项研究中，我们利用Caii 8542的光谱线研究了一个经历了两次B级耀斑的活动区色球层的振荡行为。我们分析了强度和速度的振荡，发现两者都有不同的行为。强度振荡是最普遍的活动区的太阳黑子和磁孔的本影，并在该地区的范围内，其中包含显着的振荡被发现减少时，比较时间后的耀斑之前。通过测量磁场的演变，我们发现这可能是因为随着磁场倾角的增加，本影周围的区域变得更加“半影”。速度振荡被发现在整个活动区之前和之后的耀斑，但被清楚地观察到的地区，这是由第二个耀斑变亮。通过与EUV成像的比较，可以看出，强烈的色球速度振荡与3-4分钟的周期发生在同一时间和位置作为耀斑环冷却后30分钟的第二个耀斑峰值。这可能是环中的扰动在其声学截止频率下激发色球层响应的证据。
Chromospheric oscillations can give us insight into the physical environment in the solar atmosphere, both in quiet Sun and flaring conditions. Many authors have reported increases in the prevalence of 3-minute oscillations which are thought to be excited by events which impact the chromosphere such as flares. In this study, we utilized the Caii8542 Å line to study the oscillatory behaviour of the chromosphere in an active region which underwent two B-class flares. We analysed oscillations in both intensity and velocity, and found different behaviours in both. Intensity oscillations were most prevalent over the umbrae of sunspots and magnetic pores in the active region, and the extent of the area which contained significant oscillations was found to decrease when comparing times after the flares to before. By measuring the evolution of the magnetic field, we found that this could be because the areas surrounding the umbrae were becoming more ‘penumbral’ with an increase to the magnetic field inclination. Velocity oscillations were found across the active region both before and after the flares but were observed clearly in areas which were brightened by the second flare. By comparing to EUV imaging, it was seen that strong chromospheric velocity oscillations with 3–4-minute periods occurred at the same time and location as a flare loop cooling 30 min after the second flare peak. This could be evidence of disturbances in the loop exciting a response from the chromosphere at its acoustic cut-off frequency.