论文标题
无线电爆发源大小和太阳电晕中散射的Lofar观察
LOFAR observations of radio burst source sizes and scattering in the solar corona
论文作者
论文摘要
低频无线电波散射和折射可能会对观测到的太阳能电晕中观察到的无线电源的位置产生巨大影响。散射和折射被认为是由于湍流引起的电子密度波动所致。因此，确定真实的无线电源大小可以提供有关冠状血浆中湍流的信息。但是，在低频（例如低频阵列（Lofar））上缺乏高空间分辨率无线电干涉测量值，因此很难确定真正的无线电源大小和无线电波散射水平。在这里，我们直接拟合了洛法（Lofar）对IIIB型无线电爆发的可见性，该爆发具有椭圆形的高斯，以确定其源尺寸和位置。这避免了对源的成像，然后脱离convolve lofar的点扩散函数的需求，这可以引起伪造效应，以使源大小和形状引入。对于34.76 MHz的突发，我们发现沿主要和次要轴的最高（FWHM）高度为$ 18.8^\ prime $ $ $ $ \ pm〜0.1^\ prime $和$ 10.2^\ prime $ $ $ \ pm〜0.1^\ prime $ 10.2^\ prime prime，在1.75 $ $ $ $ $ $ $ $ $ $ $ $ $ y \ y \ y \ y \ y \ y \ y \ y \ y \ y \ y \ y \ y。我们的结果表明，太阳电晕中的密度波动水平是无线电波散射的主要原因，导致源尺寸较大。但是，$ \ varepsilon $的大小可能比以前在绑定阵列图像中无线电波散射中得出的幅度小。
Low frequency radio wave scattering and refraction can have a dramatic effect on the observed size and position of radio sources in the solar corona. The scattering and refraction is thought to be due to fluctuations in electron density caused by turbulence. Hence, determining the true radio source size can provide information on the turbulence in coronal plasma. However, the lack of high spatial resolution radio interferometric observations at low frequencies, such as with the LOw Frequency ARray (LOFAR), has made it difficult to determine the true radio source size and level of radio wave scattering. Here we directly fit the visibilities of a LOFAR observation of a Type IIIb radio burst with an elliptical Gaussian to determine its source size and position. This circumvents the need to image the source and then de-convolve LOFAR's point spread function, which can introduce spurious effects to the source size and shape. For a burst at 34.76 MHz, we find full width at half maximum (FWHM) heights along the major and minor axes to be $18.8^\prime$ $\pm~0.1^\prime$ and $10.2^\prime$ $\pm~0.1^\prime$, respectively, at a plane of sky heliocentric distance of 1.75 R$_\odot$. Our results suggest that the level of density fluctuations in the solar corona is the main cause of the scattering of radio waves, resulting in large source sizes. However, the magnitude of $\varepsilon$ may be smaller than what has been previously derived in observations of radio wave scattering in tied-array images.
