Coronal Hard X-Ray Sources Revisited
Coronal Hard X-Ray Sources Revisited
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DOI：
10.3847/1538-4357/aae0f5
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发表时间：
2018-09
期刊：
影响因子：
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通讯作者：
B. Dennis;Miguel A. Duval-Poo;M. Piana;A. Inglis;A. Gordon Emslie;Jingnan Guo;Yan Xu
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文献类型：
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作者：
B. Dennis;Miguel A. Duval-Poo;M. Piana;A. Inglis;A. Gordon Emslie;Jingnan Guo;Yan Xu
本文报道了对耀斑的再分析，其中硬X射线（HXR）主要来自日冕，而不是更常见的色球足点。所有的26个先前分析的事件时间间隔，超过13耀斑，重新检查与耀斑模型的一致性，其中电子加速附近的磁环的顶部，具有足够高的密度，以阻止大多数电子库仑碰撞之前，他们可以到达的足点。在先前的分析中，特别重要的是发现日冕HXR源的长度随着能量在20-30 keV范围内的增加而增加。然而，在考虑到较高能量的足点发射影响日冕HXR源的推断长度的可能性之后，并使用抑制这种足点发射的可能影响的分析技术，我们得出结论，不再有证据表明HXR日冕源的长度随着能量的增加而增加。事实上，对于满足我们选择标准的6个耀斑和12个时间间隔，环长度在20和30 keV之间平均减少了1.0 ± 0.2 arcsec，标准差为3.5 arcsec。我们发现强有力的证据表明，随着能量的增加，日冕HXR源的峰值在海拔高度上增加。对于发射的热分量，这与标准CHSKP耀斑模型一致，其中日冕电流片中的磁重联导致在逐渐升高的高度形成新的热环。对非热发射的解释还不是很清楚。
This paper reports on the re-analysis of solar flares in which the hard X-rays (HXRs) come predominantly from the corona rather than from the more usual chromospheric footpoints. All of the 26 previously analyzed event time intervals, over 13 flares, are re-examined for consistency with a flare model in which electrons are accelerated near the top of a magnetic loop which has a sufficiently high density to stop most of the electrons by Coulomb collisions before they can reach the footpoints. Of particular importance in the previous analysis was the finding that the length of the coronal HXR source increased with energy in the 20–30 keV range. However, after allowing for the possibility that footpoint emission at the higher energies affects the inferred length of the coronal HXR source, and using analysis techniques that suppress the possible influence of such footpoint emission, we conclude that there is no longer evidence that the length of the HXR coronal sources increase with increasing energy. In fact, for the six flares and 12 time intervals that satisfied our selection criteria, the loop lengths decreased on average by 1.0 ± 0.2 arcsec between 20 and 30 keV, with a standard deviation of 3.5 arcsec. We find strong evidence that the peak of the coronal HXR source increases in altitude with increasing energy. For the thermal component of the emission, this is consistent with the standard CHSKP flare model in which magnetic reconnection in a coronal current sheet results in new hot loops being formed at progressively higher altitudes. The explanation for the nonthermal emission is not so clear.