Heating of the solar chromosphere in a sunspot light bridge by electric currents
Heating of the solar chromosphere in a sunspot light bridge by electric currents
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DOI：
10.1051/0004-6361/202141456
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发表时间：
2021-07
影响因子：
6.5
通讯作者：
R. Louis;A. Prasad;C. Beck;D. Choudhary;M. S. Yalim
中科院分区：
文献类型：
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作者：
R. Louis;A. Prasad;C. Beck;D. Choudhary;M. S. Yalim
上下文。电阻欧姆耗散被认为是加热太阳色球的一种机制，但很少有研究建立这种联系。目标。我们的目标是确定电流的欧姆耗散如何加热太阳色球。方法：研究方法。我们结合来自邓恩太阳望远镜的高分辨率光谱Ca II数据和来自日震和磁成像仪(HMI)的矢量磁场观测来研究太阳黑子光桥中的热增强。来自HMI的光球磁场是使用提供电流三维分布的非力场技术外推到日冕的，而具有局部热力学平衡和非局部热力学平衡光谱档案的色球CaII线的反演提供了从光球到色球的温度分层。结果。我们发现，光桥是一个强电流的位置，在底部边界大约0.3Am−2，电流延伸到大约0.7 mm，并且随着高度的单调减小。这些洋流产生的色球温度相对于本影超过约600−800K。只有灯桥在13h的持续时间内出现了相对较弱和高度倾斜的磁场，显示出热增强和电流的空间符合。温度提升和考林加热主要限制在光桥上方0.4−0.7 mm的高度范围内。相应增加的200J m−3的内能可由加热在约10min内提供。结论。我们的结果为洋流通过欧姆耗散加热下部太阳色球提供了直接证据。
Context. Resistive Ohmic dissipation has been suggested as a mechanism for heating the solar chromosphere, but few studies have established this association. Aims. We aim to determine how Ohmic dissipation by electric currents can heat the solar chromosphere. Methods. We combine high-resolution spectroscopic Ca II data from the Dunn Solar Telescope and vector magnetic field observations from the Helioseismic and Magnetic Imager (HMI) to investigate thermal enhancements in a sunspot light bridge. The photospheric magnetic field from HMI was extrapolated to the corona using a non-force-free field technique that provided the three-dimensional distribution of electric currents, while an inversion of the chromospheric Ca II line with a local thermodynamic equilibrium and a nonlocal thermodynamic equilibrium spectral archive delivered the temperature stratifications from the photosphere to the chromosphere. Results. We find that the light bridge is a site of strong electric currents, of about 0.3 A m−2 at the bottom boundary, which extend to about 0.7 Mm while decreasing monotonically with height. These currents produce a chromospheric temperature excess of about 600−800 K relative to the umbra. Only the light bridge, where relatively weak and highly inclined magnetic fields emerge over a duration of 13 h, shows a spatial coincidence of thermal enhancements and electric currents. The temperature enhancements and the Cowling heating are primarily confined to a height range of 0.4−0.7 Mm above the light bridge. The corresponding increase in internal energy of 200 J m−3 can be supplied by the heating in about 10 min. Conclusions. Our results provide direct evidence for currents heating the lower solar chromosphere through Ohmic dissipation.