Statistical Studies of Solar White-light Flares and Comparisons with Superflares on Solar-type Stars
Statistical Studies of Solar White-light Flares and Comparisons with Superflares on Solar-type Stars
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DOI：
10.3847/1538-4357/aa9b34
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发表时间：
2017-10
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通讯作者：
K. Namekata;Takahito Sakaue;Kyoko Watanabe;A. Asai;H. Maehara;Y. Notsu;S. Notsu;S. Honda;T. Ishii;K. Ikuta;D. Nogami;K. Shibata
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作者：
K. Namekata;Takahito Sakaue;Kyoko Watanabe;A. Asai;H. Maehara;Y. Notsu;S. Notsu;S. Honda;T. Ishii;K. Ikuta;D. Nogami;K. Shibata
近年来，在太阳型恒星上发现了许多白光耀斑（WLF）。统计研究发现，它们的能量（E）和持续时间（τ）之间存在相关性，类似于太阳硬/软X射线耀斑。这表明太阳和恒星耀斑能量释放的普遍机制，即，磁重联本文对太阳动力学天文台/HMI观测到的50个太阳WLF进行了统计研究，并研究了能量和持续时间之间的相关性。因此，太阳WLF的E-τ关系（）与恒星超耀斑的E-τ关系（）非常相似。然而，恒星超耀斑的持续时间比太阳WLF预期的短一个数量级。我们提出了以下两种解释：（1）在太阳耀斑中，WLF的冷却时间尺度可能比重联时间尺度长，并且太阳WLF的衰减时间可以通过冷却效应而延长;（2）可以通过应用磁重联理论导出的标度律（）来理解这种分布。在后一种情况下，预计观测到的超级耀斑的磁场强度比太阳耀斑强2-4倍。
Recently, many superflares on solar-type stars have been discovered as white-light flares (WLFs). The statistical study found a correlation between their energies (E) and durations (τ): , similar to those of solar hard/soft X-ray flares, . This indicates a universal mechanism of energy release on solar and stellar flares, i.e., magnetic reconnection. We here carried out statistical research on 50 solar WLFs observed with Solar Dynamics Observatory/HMI and examined the correlation between the energies and durations. As a result, the E–τ relation on solar WLFs ( ) is quite similar to that on stellar superflares ( ). However, the durations of stellar superflares are one order of magnitude shorter than those expected from solar WLFs. We present the following two interpretations for the discrepancy: (1) in solar flares, the cooling timescale of WLFs may be longer than the reconnection one, and the decay time of solar WLFs can be elongated by the cooling effect; (2) the distribution can be understood by applying a scaling law ( ) derived from the magnetic reconnection theory. In the latter case, the observed superflares are expected to have 2–4 times stronger magnetic field strength than solar flares.