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arXiv 1104.3902astro-ph.SR
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Hinode观测到的与X6 .5耀斑有关的沿中性线切变Evershed流的快速增强

Rapid Enhancement of Sheared Evershed Flow Along the Neutral Line Associated with an X6.5 Flare Observed by Hinode

Na Deng, Chang Liu, Debi Prasad Choudhary, Haimin Wang

摘要:

本文介绍了2006年12月6日由Hinode/SOT获得的NOAA AR 10930的G波段和Ca II H观测结果,其中包括一个X6.5耀斑。采用局部相关跟踪(LCT)技术,对经透视缩短校正的G波段图像序列进行处理,获取了该复杂的β-γ-δ活动区的水平自行。利用连续的高质量、空间和时间分辨率的G波段数据,我们不仅证实了外半影的快速衰减和中心结构在耀斑中性线附近的变暗,而且第一次明确地检测到剪切Evershed流的增强,(平均水平流速从330 ± 3.1 m/s增加到403 ± 4.6 m/s)。耀斑后的Ca II H图像表明,原本在中性线两侧呈扇形分布的场线被连接起来。由于半影结构和Evershed流与光球磁倾角或水平场强度密切相关,我们将黑子结构和表面流的快速变化解释为耀斑引起的磁场重组的结果。磁场由向外成扇形变为向内连接,导致外半影衰减,同时,在耀斑中性线附近的磁场变得更加水平,导致那里的Evershed流更强。中性线附近水平磁场增强的推断与最近的磁观测和耀斑引起的光球磁场变化的理论预测是一致的。

英文摘要:

We present G-band and Ca II H observations of NOAA AR 10930 obtained by Hinode/SOT on 2006 December 6 covering an X6.5 flare. Local Correlation Tracking (LCT) technique was applied to the foreshortening-corrected G-band image series to acquire horizontal proper motions in this complex beta-gamma-delta active region. With the continuous high quality, spatial and temporal resolution G-band data, we not only confirm the rapid decay of outer penumbrae and darkening of the central structure near the flaring neutral line, but also unambiguously detect for the first time the enhancement of the sheared Evershed flow (average horizontal flow speed increased from 330+-3.1 to 403+-4.6 m/s) along the neutral line right after the eruptive white-light flare. Post-flare Ca II H images indicate that the originally fanning out field lines at the two sides of the neutral line get connected. Since penumbral structure and Evershed flow are closely related to photospheric magnetic inclination or horizontal field strength, we interpret the rapid changes of sunspot structure and surface flow as the result of flare-induced magnetic restructuring down to the photosphere. The magnetic fields turn from fanning out to inward connection causing outer penumbrae decay, meanwhile those near the flaring neutral line become more horizontal leading to stronger Evershed flow there. The inferred enhancement of horizontal magnetic field near the neutral line is consistent with recent magnetic observations and theoretical predictions of flare-invoked photospheric magnetic field change.

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