THE SUB-ARCSECOND HARD X-RAY STRUCTURE OF LOOP FOOTPOINTS IN A SOLAR FLARE
THE SUB-ARCSECOND HARD X-RAY STRUCTURE OF LOOP FOOTPOINTS IN A SOLAR FLARE
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太阳耀斑环足点的亚弧秒硬X射线结构
DOI：
10.1088/0004-637x/717/1/250
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
M. Battaglia
中科院分区：
文献类型：
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作者：
E. P. Kontar;I. Hannah;N. Jeffrey;M. Battaglia
将新发展的X射线可见度前向拟合技术应用于一次临边耀斑的RHESSI数据，研究了硬X射线（HXR）色球足点源的大小、形状和位置对能量和高度的依赖性。这提供了有关电子传输和色球密度结构的信息。利用PIXON、最大熵法、CLEAN和可见度前向拟合算法分析了两个足点X射线源在20 ~ 200 keV非热能量范围内的空间分布。我们报告，第一次，垂直范围和宽度的HXR色球源测量作为一个功能的肢体事件的能量。我们的观察表明，足迹的垂直和水平尺寸都随着能量的增加而减小。更高的能量发射起源于色球层的更深处，与向下的耀斑加速流电子相一致。足点的椭圆率随能量的增加而增加，从1020 keV时的0.5增加到10150 keV时的0.9。X射线辐射的位置与尺度高度为150 km的指数密度分布相一致。HXR足点源的特征尺寸沿着肢体随能量减小，表明足点中存在会聚磁场。X射线源的垂直尺寸与单一密度尺度高度的简单碰撞输运不一致，但可以用色球层中的多线程密度结构来解释。
The newly developed X-ray visibility forward fitting technique is applied to the RHESSI data of a limb flare to investigate the energy and height dependence on sizes, shapes, and position of hard X-ray (HXR) chromospheric footpoint sources. This provides information about the electron transport and chromospheric density structure. The spatial distribution of two footpoint X-ray sources is analyzed using PIXON, Maximum Entropy Method, CLEAN, and visibility forward fit algorithms at nonthermal energies from ∼20 to ∼200 keV. We report, for the first time, the vertical extents and widths of HXR chromospheric sources measured as a function of energy for a limb event. Our observations suggest that both the vertical and horizontal sizes of footpoints are decreasing with energy. Higher energy emission originates progressively deeper in the chromosphere, consistent with downward flare accelerated streaming electrons. The ellipticity of the footpoints grows with energy from ∼0.5 at ∼20 keV to ∼0.9 at ∼150 keV. The positions of X-ray emission are in agreement with an exponential density profile of scale height ∼150 km. The characteristic size of the HXR footpoint source along the limb decreases with energy, suggesting a converging magnetic field in the footpoint. The vertical sizes of X-ray sources are inconsistent with simple collisional transport in a single density scale height but can be explained using a multi-threaded density structure in the chromosphere.