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arXiv 2404.12005astro-ph.SRastro-ph.HE
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太阳耀斑区域终止激波处相对论性电子的产生

Generation of relativistic electrons at the termination shock in the solar flare region

G. Mann, A. M. Veronig, F. Schuller

备注：
Accepted for publication in A&A
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AI总结：

本研究针对2017年9月10日X8.2级太阳耀斑，利用Rankine-Hugoniot关系评估终止激波处等离子体加热，证明激波加热产生的相对论性电子足以解释观测到的微波和硬X射线辐射。

摘要：

太阳耀斑伴随着从射电到伽马射线波段电磁辐射的增强。相关的硬X射线（HXR）和微波辐射是由高能电子产生的，这些电子携带了耀斑释放能量的相当大一部分。耀斑通常被理解为日冕中磁重联的一种表现。所谓的标准CSHKP模型是喷发耀斑最广泛接受的模型之一。2017年9月10日的太阳耀斑为研究该模型提供了独特的机会。扩展欧文斯谷太阳阵列（EOVSA）的观测显示，在耀斑区域产生了1.6×10^4个能量大于300 keV的电子。太阳射电和极紫外观测以及数值模拟中都有迹象表明，在磁重联出流区域出现了终止激波（TS）。在终止激波处加速的电子可以被认为是产生环顶HXR源的原因。与以往研究不同，我们研究了终止激波处等离子体的加热是否提供了足够的相对论性电子，以满足2017年9月10日X8.2级太阳耀斑期间观测到的HXR和微波辐射所需。我们通过利用该事件期间测量的日冕条件下的Rankine-Hugoniot关系评估激波前后的温度跳跃，研究了终止激波处等离子体的加热。在加热的下游区域计算了相对论性电子的比例。在磁重联出流区域，等离子体在终止激波处被强烈加热。因此，电子分布函数尾部有足够的高能电子，以满足该事件期间观测到的微波和HXR辐射。终止激波处相对论性电子的产生是解释耀斑期间增强的微波和HXR辐射的一种可能机制。

英文摘要：

Solar flares are accompanied by an enhanced emission of electromagnetic waves from the radio up to the gamma-ray range. The associated hard X-ray (HXR) and microwave radiation is generated by energetic electrons, which carry a substantial part of the energy released during a flare. The flare is generally understood as a manifestation of magnetic reconnection in the corona. The so-called standard CSHKP model is one of the most widely accepted models for eruptive flares. The solar flare on September 10, 2017 offers a unique opportunity to study this model. The observations from the Expanded Owens Valley Solar Array (EOVSA) show that 1.6x10^4 electrons with energies >300 keV were generated in the flare region. There are signatures in solar radio and extreme ultraviolet observations as well as numerical simulations that a termination shock (TS) appears in the magnetic reconnection outflow region. Electrons accelerated at the TS can be considered to generate the loop-top HXR sources. In contrast to previous studies, we investigate whether the heating of the plasma at the TS provides enough relativistic electrons needed for the HXR and microwave emission observed during the X8.2 solar flare on September 10, 2017. We studied the heating of the plasma at the TS by evaluating the jump in the temperature across the shock by means of the Rankine-Hugoniot relationships under coronal circumstances measured during that event. The part of relativistic electrons was calculated in the heated downstream region. In the magnetic reconnection outflow region, the plasma is strongly heated at the TS. Thus, there are enough energetic electrons in the tail of the electron distribution function needed for the microwave and HXR emission observed during that event. The generation of relativistic electrons at the TS is a possible mechanism to explain the enhanced microwave and HXR radiation emitted during flares.

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