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arXiv 1609.01463astro-ph.SR
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日冕流绳爆发期间电子加速场的射电诊断

Radio Diagnostics of Electron Acceleration Sites During the Eruption of a Flux Rope in the Solar Corona

Eoin P. Carley, Nicole Vilmer, Peter T. Gallagher

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摘要：

日冕中的电子加速通常与耀斑和被称为通量绳的扭曲磁结构的爆发有关。然而，在耀斑和喷发过程中，这种粒子加速的位置和机制仍然受到许多调查。观察粒子加速的确切位置可以帮助确认耀斑和喷发是如何开始的，以及它们是如何演变的。在这里，我们使用大气成像组件来分析2014年4月18日的耀斑和爆发通量绳，而来自Nancay射电天文设施的观测使我们能够诊断爆发期间电子加速的位置。我们的分析表明，一个预先形成的通量绳缓慢上升，并在C级耀斑，等离子体射流和>75 keV的电子从绳中心逃逸到日冕时变得不稳定的证据。随着喷发的进行，在通量绳上方持续加速能量约为5 keV的电子，持续时间超过5分钟。在耀斑峰值时，一个电子加速点位于耀斑附近，而另一个电子加速点则被喷发的通量绳以高达400 km/s的速度驱动进入日冕。然后高能电子充满喷发的体积，最终允许通量绳腿从150- 445 MHz的射电源清晰成像。根据Joshi等人（2015）的分析，我们得出结论，高能电子的位置与磁扇脊结构内部的系绳切割或通量抵消情景的通量绳喷发一致。总的来说，我们的射电观测使我们能够更好地了解通量绳喷发及其相关电子加速站点的演变，从喷发开始到传播到日冕。

英文摘要：

Electron acceleration in the solar corona is often associated with flares and the eruption of twisted magnetic structures known as flux ropes. However, the locations and mechanisms of such particle acceleration during the flare and eruption are still subject to much investigation. Observing the exact sites of particle acceleration can help confirm how the flare and eruption are initiated and how they evolve. Here we use the Atmospheric Imaging Assembly to analyse a flare and erupting flux rope on 2014-April-18, while observations from the Nancay Radio Astronomy Facility allows us to diagnose the sites of electron acceleration during the eruption. Our analysis shows evidence for a pre-formed flux rope which slowly rises and becomes destabilised at the time of a C-class flare, plasma jet and the escape of >75 keV electrons from rope center into the corona. As the eruption proceeds, continued acceleration of electrons with energies of ~5 keV occurs above the flux rope for a period over 5 minutes. At flare peak, one site of electron acceleration is located close to the flare site while another is driven by the erupting flux rope into the corona at speeds of up to 400 km/s. Energetic electrons then fill the erupting volume, eventually allowing the flux rope legs to be clearly imaged from radio sources at 150-445MHz. Following the analysis of Joshi et al. (2015), we conclude that the sites of energetic electrons are consistent with flux rope eruption via a tether-cutting or flux cancellation scenario inside a magnetic fan-spine structure. In total, our radio observations allow us to better understand the evolution of a flux rope eruption and its associated electron acceleration sites, from eruption initiation to propagation into the corona.

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