MAGNETIC RECONNECTION DURING THE TWO-PHASE EVOLUTION OF A SOLAR ERUPTIVE FLARE
MAGNETIC RECONNECTION DURING THE TWO-PHASE EVOLUTION OF A SOLAR ERUPTIVE FLARE
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DOI：
10.1088/0004-637x/706/2/1438
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发表时间：
2008-09
期刊：
影响因子：
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通讯作者：
B. Joshi;A. Veronig;K. Cho;S. Bong;Y. Moon;Jeongwoo Lee;B. Somov;P. K. Manoharan;Y. H. Kim
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文献类型：
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作者：
B. Joshi;A. Veronig;K. Cho;S. Bong;Y. Moon;Jeongwoo Lee;B. Somov;P. K. Manoharan;Y. H. Kim
我们提出了一个详细的多波长分析和解释的M7.6耀斑的演变，发生在2003年10月24日的东南边缘附近。TRACE 195耀斑前的图像显示，明亮而复杂的日冕环系统已经存在于耀斑现场。从拉马蒂高能太阳光谱成像仪（RHESSI）航天器上拍摄的耀斑X射线观测揭示了耀斑演化的两个阶段。第一阶段的特征是X射线环顶（LT）源的高度下降了10.11分钟。首次报道了如此长的下降LT源运动持续时间。位于X射线LT源下方的EUV环在此期间也以相似的速度（约15 km s-1）收缩。在第二阶段，观测到两个不同的硬X射线足点（FP）源，它们与UV和Hα耀斑带有很好的相关性。X射线LT源现在表现出从标准耀斑模型预期的向上运动。在第一阶段的RHESSI谱是软的，并指示热的热辐射从耀斑环的温度T > 25 MK在早期阶段。另一方面，在第二阶段（γ = 2.6-2.8），在高能量（ε = 25 keV）下的谱遵循硬幂律。我们发现，所观察到的LT和FP源的运动可以理解为三维磁场重联在电晕分离器的结果。在耀斑的第一阶段，重联释放出与耀斑前光球层剪切流产生的磁张力有关的过剩磁能。伴随的磁剪切在日冕中的重联过程的弛豫解释了LT源的下降运动。在第二阶段，普通的重联过程占主导地位，描述的能量释放的标准模型的大爆发耀斑的FP分离和LT源的向上运动的增加。
We present a detailed multi-wavelength analysis and interpretation of the evolution of an M7.6 flare that occurred near the southeast limb on 2003 October 24. Pre-flare images at TRACE 195 Å show that the bright and complex system of coronal loops already existed at the flaring site. The X-ray observations of the flare taken from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) spacecraft reveal two phases of the flare evolution. The first phase is characterized by the altitude decrease of the X-ray looptop (LT) source for ∼11 minutes. Such a long duration of the descending LT source motion is reported for the first time. The EUV loops, located below the X-ray LT source, also undergo contraction with similar speed (∼15 km s−1) in this interval. During the second phase the two distinct hard X-ray footpoint (FP) sources are observed which correlate well with UV and Hα flare ribbons. The X-ray LT source now exhibits upward motion as anticipated from the standard flare model. The RHESSI spectra during the first phase are soft and indicative of hot thermal emission from flaring loops with temperatures T > 25 MK at the early stage. On the other hand, the spectra at high energies (ε ≳ 25 keV) follow hard power laws during the second phase (γ = 2.6–2.8). We show that the observed motion of the LT and FP sources can be understood as a consequence of three-dimensional magnetic reconnection at a separator in the corona. During the first phase of the flare, the reconnection releases an excess of magnetic energy related to the magnetic tensions generated before a flare by the shear flows in the photosphere. The relaxation of the associated magnetic shear in the corona by the reconnection process explains the descending motion of the LT source. During the second phase, the ordinary reconnection process dominates describing the energy release in terms of the standard model of large eruptive flares with increasing FP separation and upward motion of the LT source.