论文标题
叶丝带处的虹膜Si IV线曲线作为色层凝结的指示
IRIS Si IV Line Profiles at Flare Ribbons as Indications of Chromospheric Condensation
论文作者
论文摘要
我们列出了界面区域成像光谱仪（IRIS）观察到的三种太阳耀斑中的Si IV线轮廓的时间变化。在2014年9月6日的M1.1耀斑和2014年9月10日的X1.6耀斑中，Si IV线的轮廓从完全红移到红翼随着耀斑开发而发展。但是，在2016年12月2日的B1.8耀斑中，Si IV线曲线在整个耀斑演变中都完全红移。我们使用单个高斯函数拟合全面的红移线轮廓，但具有双高斯函数的红色空气函数来推断相应的多普勒速度。此外，我们发现在25 keV上方的硬X射线发射出现在两个大耀斑中，这意味着非热电子束加热。在微叶片中，只有高达12 keV的硬X射线发射较弱，这主要表明热加热。我们将三种耀斑中Si IV系的红移或红色不对称解释为色球凝结的光谱表现。我们建议该线似乎是完全红移还是红色空气对称取决于加热机制以及凝结的传播。
We present temporal variations of the Si IV line profiles at the flare ribbons in three solar flares observed by the Interface Region Imaging Spectrograph (IRIS). In the M1.1 flare on 2014 September 6 and the X1.6 flare on 2014 September 10, the Si IV line profiles evolve from wholly redshifted to red-wing enhanced with the flare development. However, in the B1.8 flare on 2016 December 2, the Si IV line profiles are wholly redshifted throughout the flare evolution. We fit the wholly redshifted line profiles with a single Gaussian function but the red-asymmetric ones with a double Gaussian function to deduce the corresponding Doppler velocities. In addition, we find that hard X-ray emission above 25 keV shows up in the two large flares, implying a nonthermal electron beam heating. In the microflare, there only appears weak hard X-ray emission up to 12 keV, indicative of a thermal heating mostly. We interpret the redshifts or red asymmetries of the Si IV line at the ribbons in the three flares as spectral manifestations of chromospheric condensation. We propose that whether the line appears to be wholly redshifted or red-asymmetric depends on the heating mechanisms and also on the propagation of the condensation.
