The magnetic topology of the inverse Evershed flow
The magnetic topology of the inverse Evershed flow
复制标题
逆Evershed流的磁拓扑
DOI：
10.1051/0004-6361/202142585
复制
发表时间：
2022
影响因子：
6.5
通讯作者：
Hu, Q.
中科院分区：
文献类型：
--
作者：
Prasad, A.;Ranganathan, M.;Beck, C.;Choudhary, D. P.;Hu, Q.
背景反向Evershed流（IEF）是色球层高度上朝向太阳黑子的质量运动，目的结合Dunn太阳望远镜对NOAA 12418的高分辨率观测和日震磁成像仪（HMI）的矢量磁场测量，确定IEF的驱动因素。HMI数据被用于非无力磁场外推，以跟踪活动区太阳黑子附近的闭合磁力线。我们确定了它们的长度和高度，位于其内部和外部的脚点，并推导出流速沿着them.ResultsThe磁场线有关的IEF达到平均高度为3兆赫兹（毫米）超过13毫米的长度。内（外）脚点位于1.2（1.9）太阳黑子半径。内、外足点的平均场强差Δ B为+400 G。温差Δ T与Δ B反相关，平均值为−100 K。由ΔBand主导的压力差Δpis主要为正，朝向内足点的驱动力平均为1.7 kPa。从Δ预测的速度preproduce LOS速度的2-10公里s-1的平方根dependency.ConclusionsWe发现，IEF驱动沿着磁场线连接网络元素与外部半影的气体压力差，结果从不同的磁场强度预测的经典虹吸流的情况。
ContextThe inverse Evershed flow (IEF) is a mass motion towards sunspots at chromospheric heights.AimsWe combined high-resolution observations of NOAA 12418 from the Dunn Solar Telescope and vector magnetic field measurements from the Helioseismic and Magnetic Imager (HMI) to determine the driver of the IEF.MethodsWe derived chromospheric line-of-sight (LOS) velocities from spectra of Hαand Ca II IR. The HMI data were used in a non-force-free magnetic field extrapolation to track closed field lines near the sunspot in the active region. We determined their length and height, located their inner and outer foot points, and derived flow velocities along them.ResultsThe magnetic field lines related to the IEF reach on average a height of 3 megameter (Mm) over a length of 13 Mm. The inner (outer) foot points are located at 1.2 (1.9) sunspot radii. The average field strength difference ΔBbetween inner and outer foot points is +400 G. The temperature difference ΔTis anti-correlated with ΔBwith an average value of −100 K. The pressure difference Δpis dominated by ΔBand is primarily positive with a driving force towards the inner foot points of 1.7 kPa on average. The velocities predicted from Δpreproduce the LOS velocities of 2–10 km s−1with a square-root dependence.ConclusionsWe find that the IEF is driven along magnetic field lines connecting network elements with the outer penumbra by a gas pressure difference that results from a difference in field strength as predicted by the classical siphon flow scenario.