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首页> 外文期刊>Solar physics >Centre-to-Limb Brightness Variations from the Atacama Large Millimeter-Submillimeter Array (ALMA) Full-Disk Solar Images
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Centre-to-Limb Brightness Variations from the Atacama Large Millimeter-Submillimeter Array (ALMA) Full-Disk Solar Images

机译：ATACAMA大毫米 - 亚倍数钟阵列（ALMA）全磁盘太阳能图像的中心至肢亮度变化

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Science Verification (SV) data of solar observations with the Atacama Large Millimeter-submillimeter Array (ALMA) telescope have been released to the scientific community. Understanding the centre-to-limb brightness function is necessary to compare features in full-disk images. Our goals are to find the empirical centre-to-limb brightness functions in two available spectral bands and create flattened images with centre-to-limb brightness variations removed. We used a second-order polynomial fit of the cosine of incidence angle to data points as a function of radial distance to the centre of the solar disk. The method also includes iterative removal of outliers based on the inter-quartile range. Fitting functions for all available images proved to describe the data adequately with comparatively small errors in the fitting coefficients. In both bands we found brightening towards the limb, which is a consequence of the increase in electron temperature with radial distance in this region of the solar atmosphere. This study found that the brightness temperature [T_b] of an active region has about 180 K difference between estimates with and without the limb brightening at radial distance ≈0.75 R_⊙ in Band 6.We also made flattened images with limb brightening removed. The limb-brightening effect in ALMA images is significant enough (of the order of 10% for Band 3 and about 15% in Band 6) that it cannot be neglected in further analyses. Since the effect of the side lobes was not included in this study, these values probably represent the lower limit of the limb brightening. The shape of the limb-brightening function can also be used to constrain electron densities and temperatures in various layers of the solar atmosphere.
机译：与Atacama大型毫米 - 亚米计阵列（ALMA）望远镜的太阳能观测的科学验证（SV）数据被释放到科学界。理解中心到肢体亮度函数必须在全磁盘图像中比较功能。我们的目标是在两种可用光谱频带中找到经验中心到肢体亮度函数，并在删除中断的亮度亮度变化的扁平图像。我们使用余弦的二阶多项式拟合到数据点作为径向距离到太阳能盘的中心的函数。该方法还包括基于四分位数范围的异常值迭代除去异常值。用于所有可用图像的拟合功能证明，在拟合系数中具有相对小的误差来描述数据。在我们发现朝向肢体的两个带中，这是太阳能大气的该区域的径向距离的电子温度增加的结果。该研究发现，有源区的亮度温度η与径向距离在频段内径向距离的估计和没有肢体的估计之间的差异约为180k差异。我们还制造了用肢体亮化的扁平图像移除。在ALMA图像中的肢体增白效果足够致意（带3的频带3的10％，带6的约15％），在进一步分析中不能忽略它。由于本研究未包括侧瓣的效果，因此这些值可能代表肢体亮的下限。肢体增白功能的形状也可用于限制太阳气氛的各个层中的电子密度和温度。

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