论文标题
2017年8月21日在太阳日食中获得图像的冠状电子密度
Coronal Electron Densities derived with Images acquired during the 21 August 2017 Total Solar Eclipse
论文作者
论文摘要
使用配备有线性偏振滤波器的数字单镜头反射（DSLR）摄像头观察到了2017年8月21日的日食。开发了一种方法，以结合获得15个不同曝光时间（从1/4000秒到4秒）的图像，在每个像素中识别检测器线性的最佳间隔。太阳能电晕的产生的镶嵌图像可扩展到5个以上的太阳半径，预计的像素大小为3.7 arcsec/Pixel，并通过10.2 Arcsecs的有效图像分辨率，并用可见的$α-$ leo leo和$ν-$ leo星星确定。图像分析表明，在内部电晕中，强度梯度是如此陡峭，以至于附近的像素显示相对强度的差异高达$ \ sim 10 \％$;这意味着在分析用极化摄像机获得的单个暴露时必须谨慎。 已经分析了具有两个不同方向的图像，以得出线性极化程度，并在太阳能电晕中获得偏振亮度$ pb $。 K-COR仪器对Mauna LOA太阳能天文台（MLSO）进行$ PB $测量进行了校准后，数据分析提供了2D冠状电子密度分布，从1.1至$ \ sim 3 $太阳RADII。还具有完整的太阳图像，并具有可见的恒星大小，也进行了绝对的辐射校准。所得的绝对校准表明，相对于MLSO，因子$ \ sim 2 $的分歧；有趣的是，这是最近发现的Eclipse预测MHD数值模拟的分歧。
The total solar eclipse of August 21st, 2017 was observed with a Digital Single Lens Reflex (DSLR) camera equipped with a linear polarizing filter. A method was developed to combine images acquired with 15 different exposure times (from 1/4000 sec to 4 sec), identifying in each pixel the best interval of detector linearity. The resulting mosaic image of the solar corona extends up to more than 5 solar radii, with a projected pixel size by 3.7 arcsec/pixel, and an effective image resolution by 10.2 arcsecs, as determined with visible $α-$Leo and $ν-$Leo stars. Image analysis shows that in the inner corona the intensity gradients are so steep, that nearby pixels shows a relative intensity difference by up to $\sim 10 \%$; this implies that careful must be taken when analyzing single exposures acquired with polarization cameras. Images acquired with two different orientations of the polarizer have been analyzed to derive the degree of linear polarization, and the polarized brightness $pB$ in the solar corona. After inter-calibration with $pB$ measurements by the K-Cor instrument on Mauna Loa Solar Observatory (MLSO), data analysis provided the 2D coronal electron density distribution from 1.1 up to $\sim 3$ solar radii. The absolute radiometric calibration was also performed, with the full sun image, and with magnitudes of visible stars. The resulting absolute calibrations show a disagreement by a factor $\sim 2$ with respect to MLSO; interestingly, this is the same disagreement recently found with eclipse predictions provided by MHD numerical simulations.
