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arXiv 1709.09472astro-ph.SR
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来自单个活动区的太阳耀斑的准周期脉动性质

Properties of quasi-periodic pulsations in solar flares from a single active region

C. E. Pugh, V. M. Nakariakov, A. -M. Broomhall, A. V. Bogomolov, I. N. Myagkova

备注：
23 pages, 57 figures. Accepted for publication by Astronomy & Astrophysics
发表信息：
A&A 608, A101 (2017)
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摘要：

我们调查的一组太阳耀斑起源于一个单一的活动区（AR），表现出QPP的属性，并寻找与AR属性的QPP周期的迹象。被研究的AR，最著名的是NOAA 12192，寿命非常长，产生了181次耀斑。来自GOES、EVE、Fermi、Vernov和NoRH天文台的数据被用来确定耀斑中是否存在QPP。对于软X射线GOES和EVE数据，使用信号的时间导数。检查时间序列数据的功率谱（没有任何形式的去趋势），将谱中峰值高于95%置信水平的耀斑标记为具有候选QPP。考虑到不确定性和可能存在的红噪声，确定了置信水平。使用HMI视线磁图确定AR特性。总共有37个耀斑（占样本的20%）显示出有QPP的良好证据，其中一些脉动可以在多个仪器和不同波段的数据中看到。QPP周期与耀斑振幅和持续时间的相关性较弱，但这可能是由于观测偏差造成的。一个更强的相关性被发现之间的QPP周期和QPP信号的持续时间，这可以部分但不完全解释观测的限制。未发现与AR面积、双极分离或平均磁场强度相关。事实上，相当一部分的耀斑样本显示QPP的证据，使用严格的检测方法与最小的数据处理表明，这些QPP是一个真实的现象，这不能解释的存在红噪声或叠加的多个不相关的耀斑。QPP周期和AR属性之间缺乏相关性意味着AR的小尺度结构是重要的，和/或不同的QPP机制在不同的情况下起作用。

英文摘要：

We investigate the properties of a set of solar flares originating from a single active region (AR) that exhibit QPPs, and look for signs of the QPP periods relating to AR properties. The AR studied, best known as NOAA 12192, was unusually long-lived and produced 181 flares. Data from the GOES, EVE, Fermi, Vernov and NoRH observatories were used to determine if QPPs were present in the flares. For the soft X-ray GOES and EVE data, the time derivative of the signal was used. Power spectra of the time series data (without any form of detrending) were inspected, and flares with a peak above the 95% confidence level in the spectrum were labelled as having candidate QPPs. The confidence levels were determined taking account of uncertainties and the possible presence of red noise. AR properties were determined using HMI line of sight magnetograms. A total of 37 flares (20% of the sample) show good evidence of having QPPs, and some of the pulsations can be seen in data from multiple instruments and in different wavebands. The QPP periods show a weak correlation with the flare amplitude and duration, but this may be due to an observational bias. A stronger correlation was found between the QPP period and duration of the QPP signal, which can be partially but not entirely explained by observational constraints. No correlations were found with the AR area, bipole separation, or average magnetic field strength. The fact that a substantial fraction of the flare sample showed evidence of QPPs using a strict detection method with minimal processing of the data demonstrates that these QPPs are a real phenomenon, which cannot be explained by the presence of red noise or the superposition of multiple unrelated flares. The lack of correlation between the QPP periods and AR properties implies that the small-scale structure of the AR is important, and/or that different QPP mechanisms act in different cases.

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