KAPPA DISTRIBUTION MODEL FOR HARD X-RAY CORONAL SOURCES OF SOLAR FLARES
KAPPA DISTRIBUTION MODEL FOR HARD X-RAY CORONAL SOURCES OF SOLAR FLARES
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DOI：
10.1088/0004-637x/764/1/6
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发表时间：
2012-12
期刊：
影响因子：
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通讯作者：
M. Oka;S. Ishikawa;P. Saint-Hilaire;S. Krucker;R. Lin
中科院分区：
文献类型：
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作者：
M. Oka;S. Ishikawa;P. Saint-Hilaire;S. Krucker;R. Lin
太阳耀斑产生硬X射线辐射，其光子谱通常由热分布和幂律分布的组合表示。然而，非热电子的数量和总能量的估计是敏感的幂律截止能量的确定。在这里，我们重新审视了2007年12月31日RHESSI观测到的“环上”日冕源，并表明Kappa分布模型也可以用来拟合其光谱。由于kappa分布除了具有高能量幂律尾之外还具有麦克斯韦样核，因此可以在不假设截止能量的情况下导出瞬时电子的发射量度和温度。此外，电子数/能量密度的非热分数可以唯一地估计，因为它们是仅幂律指数的函数。根据卡帕分布模型，我们估计日冕源区的总电子密度为2.4 × 1010 cm−3。我们还估计，在不假设源体积的情况下，源区中的中等比例（约20%）的电子是非热的，并携带总电子能量的约52%。温度为28 MK，电子密度分布的幂律指数δ为−4.3。这些结果进行了比较，传统的幂律模型和没有一个热核心组件。
Solar flares produce hard X-ray emission, the photon spectrum of which is often represented by a combination of thermal and power-law distributions. However, the estimates of the number and total energy of non-thermal electrons are sensitive to the determination of the power-law cutoff energy. Here, we revisit an “above-the-loop” coronal source observed by RHESSI on 2007 December 31 and show that a kappa distribution model can also be used to fit its spectrum. Because the kappa distribution has a Maxwellian-like core in addition to a high-energy power-law tail, the emission measure and temperature of the instantaneous electrons can be derived without assuming the cutoff energy. Moreover, the non-thermal fractions of electron number/energy densities can be uniquely estimated because they are functions of only the power-law index. With the kappa distribution model, we estimated that the total electron density of the coronal source region was ∼2.4 × 1010 cm−3. We also estimated without assuming the source volume that a moderate fraction (∼20%) of electrons in the source region was non-thermal and carried ∼52% of the total electron energy. The temperature was 28 MK, and the power-law index δ of the electron density distribution was −4.3. These results are compared to the conventional power-law models with and without a thermal core component.