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The effect of a solar flare on chromospheric oscillations
Monthly Notices of the Royal Astronomical Society ( IF 4.7 ) Pub Date : 2021-03-03 , DOI: 10.1093/mnras/stab642
David C L Millar 1 , Lyndsay Fletcher 1, 2 , Ryan O Milligan 1, 3
Affiliation  

Oscillations in the solar atmosphere have long been observed both in quiet conditions and during solar flares. The chromosphere is known for its 3-min signals, which are strong over sunspot umbrae, and have periods determined by the chromosphere’s acoustic cut-off frequency. A small number of observations have shown the chromospheric signals to be affected by energetic events such as solar flares, however the link between flare activity and these oscillations remains unclear. In this work, we present evidence of changes to the oscillatory structure of the chromosphere over a sunspot which occurs during the impulsive phase of an M1 flare. Using imaging data from the CRISP instrument across the H α and Ca ii 8542 Å spectral lines, we employed a method of fitting models to power spectra to produce maps of where there is evidence of oscillatory signals above a red-noise background. Comparing results taken before and after the impulsive phase of the flare, we found that the oscillatory signals taken after the start of the flare differ in two ways: the locations of oscillatory signals had changed and the typical periods of the oscillations had tended to increase (in some cases increasing from <100 s to ∼200 s). Both of these results can be explained by a restructuring of the magnetic field in the chromosphere during the flare activity, which is backed up by images of coronal loops showing clear changes to magnetic connectivity. These results represent one of the many ways that active regions can be affected by solar flares.

中文翻译:

太阳耀斑对色球振荡的影响

长期以来,无论是在安静条件下还是在太阳耀斑期间,都可以观察到太阳大气中的振荡。色球层以其 3 分钟的信号而闻名,这些信号在太阳黑子本影上很强,并且其周期由色球层的声学截止频率决定。少数观测表明色球信号会受到太阳耀斑等高能事件的影响,但耀斑活动与这些振荡之间的联系仍不清楚。在这项工作中,我们提供了在 M1 耀斑的脉冲阶段发生的太阳黑子上色球的振荡结构发生变化的证据。使用来自 CRISP 仪器的跨 H α 和 Ca ii 8542 Å 光谱线的成像数据,我们采用了一种将模型拟合到功率谱的方法,以生成在红噪声背景之上有振荡信号迹象的地图。对比耀斑脉冲阶段前后的结果,我们发现耀斑开始后的振荡信号在两个方面有所不同:振荡信号的位置发生了变化,典型的振荡周期趋于增加(在某些情况下,从<100 s 增加到 ∼200 s)。这两个结果都可以通过耀斑活动期间色球层中的磁场重构来解释,这得到了日冕环图像的支持,这些图像显示出磁连通性的明显变化。这些结果代表了活动区域可能受到太阳耀斑影响的众多方式之一。对比耀斑脉冲阶段前后的结果,我们发现耀斑开始后的振荡信号在两个方面有所不同:振荡信号的位置发生了变化,典型的振荡周期趋于增加(在某些情况下,从<100 s 增加到 ∼200 s)。这两个结果都可以通过耀斑活动期间色球层中的磁场重构来解释,这得到了日冕环图像的支持,这些图像显示出磁连通性的明显变化。这些结果代表了活动区域可能受到太阳耀斑影响的众多方式之一。对比耀斑脉冲阶段前后的结果,我们发现耀斑开始后的振荡信号在两个方面有所不同:振荡信号的位置发生了变化,典型的振荡周期趋于增加(在某些情况下,从<100 s 增加到 ∼200 s)。这两个结果都可以通过耀斑活动期间色球层中的磁场重构来解释,这得到了日冕环图像的支持,这些图像显示出磁连通性的明显变化。这些结果代表了活动区域可能受到太阳耀斑影响的众多方式之一。振荡信号的位置发生了变化,典型的振荡周期趋于增加(在某些情况下从<100 s增加到~200 s)。这两个结果都可以通过耀斑活动期间色球层中的磁场重构来解释,这得到了日冕环图像的支持,这些图像显示出磁连通性的明显变化。这些结果代表了活动区域可能受到太阳耀斑影响的众多方式之一。振荡信号的位置发生了变化,典型的振荡周期趋于增加(在某些情况下从<100 s增加到~200 s)。这两个结果都可以通过耀斑活动期间色球层中的磁场重构来解释,这得到了日冕环图像的支持,这些图像显示出磁连通性的明显变化。这些结果代表了活动区域可能受到太阳耀斑影响的众多方式之一。
更新日期:2021-03-03
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