The Magnetic Response of the Solar Atmosphere to Umbral Flashes
The Magnetic Response of the Solar Atmosphere to Umbral Flashes
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DOI：
10.3847/1538-4357/aab366
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发表时间：
2018-02
期刊：
影响因子：
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通讯作者：
S. J. Houston;D. Jess;A. A. Ramos-A.;A. A. Ramos-A.;S. Grant;C. Beck;Aimee A. Norton;S. Prasad
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文献类型：
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作者：
S. J. Houston;D. Jess;A. A. Ramos-A.;A. A. Ramos-A.;S. Grant;C. Beck;Aimee A. Norton;S. Prasad
太阳黑子本影的色球观测提供了一个特殊的磁声冲击现象及其对周围磁主导等离子体的影响。我们采用同步狭缝光谱偏振和光谱成像观测的色球He i 10830和Ca ii 8542线，检查在本影磁场的波动所造成的陡峭的磁声波到本影闪光。现代反演程序的应用程序后，我们发现的证据支持的情况下，本影冲击事件导致的嵌入的磁场线的膨胀，由于绝热压力的增加。利用大数统计量，我们计算出色球本影位置的绝热指数γ = 1.12 ± 0.01。对垂直于太阳法线的矢量磁场波动的检查显示，在本影闪光的位置，变化高达10200 G。这种横向磁场波动以前没有描述过。通过与非线性无力场外推的比较，我们发现横向场分量的扰动与静态场几何的方向相同。这意味着，由本影闪光产生的磁场增强是沿着发展中激波的运动路径定向的，因此在磁场的倾角和/或方位角方向上产生相对较小的变化，最大可达108 °。重要的是，这项工作强调了本影闪光能够修改全矢量磁场，通过高分辨率数据结合现代反演程序可以检测较弱的横向磁场分量。
Chromospheric observations of sunspot umbrae offer an exceptional view of magnetoacoustic shock phenomena and the impact they have on the surrounding magnetically dominated plasma. We employ simultaneous slit-based spectro-polarimetry and spectral imaging observations of the chromospheric He i 10830 Å and Ca ii 8542 Å lines to examine fluctuations in the umbral magnetic field caused by the steepening of magnetoacoustic waves into umbral flashes. Following the application of modern inversion routines, we find evidence to support the scenario that umbral shock events cause expansion of the embedded magnetic field lines due to the increased adiabatic pressure. The large number statistics employed allow us to calculate the adiabatic index, γ = 1.12 ± 0.01, for chromospheric umbral locations. Examination of the vector magnetic field fluctuations perpendicular to the solar normal revealed changes up to ∼200 G at the locations of umbral flashes. Such transversal magnetic field fluctuations have not been described before. Through comparisons with nonlinear force-free field extrapolations, we find that the perturbations of the transverse field components are oriented in the same direction as the quiescent field geometries. This implies that magnetic field enhancements produced by umbral flashes are directed along the motion path of the developing shock, hence producing relatively small changes, up to a maximum of ∼8°, in the inclination and/or azimuthal directions of the magnetic field. Importantly, this work highlights that umbral flashes are able to modify the full vector magnetic field, with the detection of the weaker transverse magnetic field components made possible by high-resolution data combined with modern inversion routines.