Sustained Heating of the Chromosphere and Transition Region Over a Sunspot Light Bridge
Sustained Heating of the Chromosphere and Transition Region Over a Sunspot Light Bridge
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DOI：
10.3847/1538-4357/aca612
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发表时间：
2023-01
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影响因子：
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通讯作者：
R. Louis;S. Mathew;A. R. Bayanna;C. Beck;D. Choudhary
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作者：
R. Louis;S. Mathew;A. R. Bayanna;C. Beck;D. Choudhary
太阳黑子光桥(LBS)在色球和过渡区表现出广泛的短寿命现象。相比之下，我们使用多用途太阳望远镜(MAST)、界面区域成像光谱仪(IRIS)、HINODE、大气成像组件(AIA)和日震和磁成像仪(HMI)的数据来分析规则太阳黑子中一个LB中持续数天的加热。用非局域热力学平衡反演法从Mast Ca II和IRIS Mg II谱线反演了色球温度。谱线宽度、多普勒频移和强度是使用高斯拟合法从IRIS谱线中得出的。日冕温度是通过差分发射测量来估计的，而日冕磁场是由HMI矢量场的外推得到的。在光球层，LB呈颗粒状，场强约为400G，无明显电流。太阳黑子没有碎裂，黑子在几天内保持稳定。在8000K到2.5MK的温度范围内，色球温度、IRIS谱线强度和宽度以及AIA 171和211ä强度都在LB中得到了增强。光球等离子体的运动仍然很小，而色球和过渡区主要是红移5-20公里的S−1，偶尔也有超过100公里的超音速下沉气流S−1。在LB上空的过剩热能约为3.2×1026erg，与辐射损失相符。它可以由太阳黑子的磁通量损失(7.5×1027erg)，来自LB宽度增加的动能(4×1028erg)，或沿冕环的质量自由落体(6.3×1026erg)提供。
Sunspot light bridges (LBs) exhibit a wide range of short-lived phenomena in the chromosphere and transition region. In contrast, we use here data from the Multi-Application Solar Telescope (MAST), the Interface Region Imaging Spectrograph (IRIS), Hinode, the Atmospheric Imaging Assembly (AIA), and the Helioseismic and Magnetic Imager (HMI) to analyze the sustained heating over days in an LB in a regular sunspot. Chromospheric temperatures were retrieved from the MAST Ca ii and IRIS Mg ii lines by nonlocal thermodynamic equilibrium inversions. Line widths, Doppler shifts, and intensities were derived from the IRIS lines using Gaussian fits. Coronal temperatures were estimated through the differential emission measure, while the coronal magnetic field was obtained from an extrapolation of the HMI vector field. At the photosphere, the LB exhibits a granular morphology with field strengths of about 400 G and no significant electric currents. The sunspot does not fragment, and the LB remains stable for several days. The chromospheric temperature, IRIS line intensities and widths, and AIA 171 and 211 Å intensities are all enhanced in the LB with temperatures from 8000 K to 2.5 MK. Photospheric plasma motions remain small, while the chromosphere and transition region indicate predominantly redshifts of 5–20 km s−1 with occasional supersonic downflows exceeding 100 km s−1. The excess thermal energy over the LB is about 3.2 × 1026 erg and matches the radiative losses. It could be supplied by magnetic flux loss of the sunspot (7.5 × 1027 erg), kinetic energy from the increase in the LB width (4 × 1028 erg), or freefall of mass along the coronal loops (6.3 × 1026 erg).