Sizes and Shapes of Sources in Solar Metric Radio Bursts
Sizes and Shapes of Sources in Solar Metric Radio Bursts
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DOI：
10.3847/1538-4357/ac3bb7
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发表时间：
2021-11
期刊：
影响因子：
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通讯作者：
M. Gordovskyy;E. P. Kontar;D. L. Clarkson;N. Chrysaphi;P. K. Browning
中科院分区：
文献类型：
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作者：
M. Gordovskyy;E. P. Kontar;D. L. Clarkson;N. Chrysaphi;P. K. Browning
来自太阳的米波和十米波射电辐射是关于日冕上部非热电子动力学的唯一直接信息来源。此外，低频射电源的光谱和成像（大小，形状和位置）观测的组合可以用作探测日冕和内日光层等离子体湍流的独特诊断工具。低频源的几何形状及其随频率的变化仍然不清楚，主要是由于太阳观测的空间分辨率相对较低。在这里，我们报告的第一个详细的多频分析的大小的太阳射电源观测的低频阵列。此外，我们调查的来源形状近似的强度分布，使用二维高斯分布与椭圆半极大轮廓。这些测量是通过一种新的经验方法来实现的，该方法用于根据已知源观测来评估仪器和电离层对无线电地图的影响。得到的源的反卷积大小被发现是小于以前的估计，往往表现出更高的椭圆率。使用二维高斯近似推断的源的大小和椭圆度，以及它们随频率的变化是一致的各向异性的无线电波散射模型在太阳日冕。
Metric and decametric radio emissions from the Sun are the only direct source of information about the dynamics of nonthermal electrons in the upper corona. In addition, the combination of spectral and imaging (sizes, shapes, and positions) observations of low-frequency radio sources can be used as a unique diagnostic tool to probe plasma turbulence in the solar corona and inner heliosphere. The geometry of the low-frequency sources and its variation with frequency are still not understood, primarily due to the relatively low spatial resolution available for solar observations. Here we report the first detailed multifrequency analysis of the sizes of solar radio sources observed by the Low Frequency Array. Furthermore, we investigate the source shapes by approximating the derived intensity distributions using 2D Gaussian profiles with elliptical half-maximum contours. These measurements have been made possible by a novel empirical method for evaluating the instrumental and ionospheric effects on radio maps based on known source observations. The obtained deconvolved sizes of the sources are found to be smaller than previous estimations, and often show higher ellipticity. The sizes and ellipticities of the sources inferred using 2D Gaussian approximation, and their variation with frequency are consistent with models of anisotropic radio-wave scattering in the solar corona.