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arXiv 1111.4248astro-ph.SR
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CME尾流中电流片底部的X射线发射

X-ray emission from the base of a current sheet in the wake of a CME

Pascal Saint-Hilaire, Sam Krucker, Robert P. Lin

摘要:

在2002年11月26日开始的CME之后,拉马迪高能太阳光谱成像仪RHESSI在光球上方0.1至0.3 RS的高度上观测了12小时的太阳边缘上方的X射线源。在整个事件中,GOES基线非常高。X射线源的温度在10-11 MK左右达到峰值,并且其发射测量在整个时间间隔内增加。在更高的位置,在0.7 RS,热(最初>8 MK)等离子体已经被SoHO上的Udron观察了2.3天。这种热等离子体被解释为跟随CME的电流片的特征(Bemporad等人,2006)。X射线源的热能含量比电流片中的热能含量大一个数量级以上。因此,它可能是电流片中的热等离子体的来源,尽管电流片通过其内部的磁重联加热不能被忽视。为了更好地表征X射线光谱,我们使用了新的技术(基于反投影和基于可分辨性)的长积分(几个小时)成像光谱。没有观察到非热硬X射线韧致辐射,导致的结论是,要么有非常小的粒子加速发生在附近的这个后弧X射线源,或者要么光子光谱指数将不得不是非典型的(在耀斑用语)高(伽马>= 8)和/或低能量截止?非常低(Ec <= 6 keV)。

英文摘要:

Following a CME which started on 2002 November 26, RHESSI, the Ramaty High Energy Solar Spectroscopic Imager, observed for 12 hours an X-ray source above the solar limb, at altitudes between 0.1 and 0.3 RS above the photosphere. The GOES baseline was remarkably high throughout this event. The X-ray source's temperature peaked around 10-11 MK, and its emission measure increased throughout this time interval. Higher up, at 0.7 RS, hot (initially >8 MK) plasma has been observed by UVCS on SoHO for 2.3 days. This hot plasma was interpreted as the signature of a current sheet trailing the CME (Bemporad et al. 2006). The thermal energy content of the X-ray source is more than an order of magnitude larger than in the current sheet. Hence, it could be the source of the hot plasma in the current sheet, although current sheet heating by magnetic reconnection within it cannot be discounted. To better characterize the X-ray spectrum, we have used novel techniques (back-projection based and visibility-based) for long integration (several hours) imaging spectroscopy. There is no observed non-thermal hard X-ray bremsstrahlung emission, leading to the conclusion that there is either very little particle acceleration occurring in the vicinity of this post- are X-ray source, or that either the photon spectral index would have had to be uncharacteristically (in flare parlance) high (gamma >= 8) and/or the low-energy cutoff? very low (Ec <= 6 keV).

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