Localized Acceleration of Energetic Particles by a Weak Shock in the Solar Corona
Localized Acceleration of Energetic Particles by a Weak Shock in the Solar Corona
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DOI：
10.3847/1538-4357/ac1cdf
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发表时间：
2021-08
期刊：
影响因子：
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通讯作者：
D. Long;H. Reid;G. Valori;J. O’Kane
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文献类型：
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作者：
D. Long;H. Reid;G. Valori;J. O’Kane
长期以来，人们一直在研究日冕中全球传播的冲击波，以量化它们对高能粒子加速的影响。然而，这项工作往往集中在与强烈的太阳耀斑和快速日冕物质抛射（CME）相关的大型事件上，其中波的速度足够快，可以轻松地将粒子加速到高能量。在这里，我们提出的粒子加速与全球波事件发生在2011年10月1日的观测。使用差分辐射测量分析，发现整体激波非常弱，阿尔文马赫数为1.008-1.013。尽管如此，南赛射电日像仪在激波阵面附近的不同位置观测到了空间分辨的iii型射电辐射，这表明高能电子的局部加速。利用磁场外推法的进一步研究确定了位于源活动区上方的磁零下方的扇结构，喷发的CME包含在这个拓扑特征中。我们提出，重新配置的日冕磁场驱动的爆发日冕物质抛射使弱冲击加速粒子沿沿着场线最初包含在风扇，随后开放到日光层，产生所观察到的类型iii的排放。这些结果表明，即使是太阳日冕中微弱的全球冲击也可以通过周围磁场的重新配置来加速高能粒子。
Globally propagating shocks in the solar corona have long been studied to quantify their involvement in the acceleration of energetic particles. However, this work has tended to focus on large events associated with strong solar flares and fast coronal mass ejections (CMEs), where the waves are sufficiently fast to easily accelerate particles to high energies. Here we present observations of particle acceleration associated with a global wave event which occurred on 2011 October 1. Using differential emission measure analysis, the global shock wave was found to be incredibly weak, with an Alfvén Mach number of ∼1.008–1.013. Despite this, spatially resolved type iii radio emission was observed by the Nançay RadioHeliograph at distinct locations near the shock front, suggesting localized acceleration of energetic electrons. Further investigation using magnetic field extrapolation identified a fan structure beneath a magnetic null located above the source active region, with the erupting CME contained within this topological feature. We propose that a reconfiguration of the coronal magnetic field driven by the erupting CME enabled the weak shock to accelerate particles along field lines initially contained within the fan and subsequently opening into the heliosphere, producing the observed type iii emission. These results suggest that even weak global shocks in the solar corona can accelerate energetic particles via reconfiguration of the surrounding magnetic field.