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arXiv 2403.14532astro-ph.SR
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近边缘太阳黑子磁性的高度依赖性

The dependence of the magnetism of a near-limb sunspot on height

M. Benko, H. Balthasar, P. Gömöry, C. Kuckein, S. J. González Manrique

AI总结:

本文利用 GRIS/GREGOR 的 spectropolarimetric 观测和谱线反演,研究近边缘稳定太阳黑子从光球到色球的磁场高度依赖性,首次直接确定 He I 1083 nm 谱线形成高度为光球上方 970 km,并揭示本影与半影中不同磁场分量随高度的变化规律。

摘要:

太阳黑子的物理参数尚未被完全理解,尤其是磁场随高度的变化。迄今为止,He I 1083 nm 谱线究竟形成于哪些高度仍是一个悬而未决的问题。我们的目标是研究太阳黑子上方大气中从光球层到色球层的磁性和动力学性质。我们利用 GREGOR 上的 GRIS 获得的 spectropolarimetric 观测数据,分析了 2016 年 6 月 20 日活动区 AR 12553 中一个稳定太阳黑子的光球层和色球层磁场性质。采用光谱线反演技术从完整 Stokes 轮廓中推断磁场矢量和多普勒速度。总共反演了三条谱线,并利用径向圆的平均值来量化磁性质的变化。该太阳黑子位于太阳边缘附近,因此使我们能够从几何上确定 He I 1083 nm 谱线的高度。我们直接通过对一个稳定太阳黑子的观测发现,氦谱线的高度位于光球谱线上方 970 km 处。总磁场强度在太阳黑子上方随高度减小;本影的减小率为 -0.34 G/km,半影的减小率为 -0.28 G/km。在本影中,倾角随高度增加而增大,但在半影中倾角随高度增加而减小。在本影中,垂直分量($B_z$)随高度减小,而水平分量($B_{hor}$)几乎保持不变。在半影中情况相反,$B_z$ 随高度几乎保持不变,而 $B_{hor}$ 减小。我们还在黑子中心侧的小尺度色球斑块中观测到 30 km/s 的快速速度。太阳黑子中随高度变化的关键参数是本影磁场的 $B_z$ 分量和半影磁场的 $B_{hor}$ 分量。

英文摘要:

The physical parameters of the sunspot are not fully understood, especially the height dependence of the magnetic field. So far, it is also an open question as to which heights the He I 1083 nm spectral line is formed at. Our aim is to investigate the magnetic and dynamical properties in the atmosphere above a sunspot, from the photosphere to the chromosphere. We analyzed the photospheric and chromospheric magnetic field properties of a stable sunspot in AR 12553 on June 20, 2016 using spectropolarimetric observations obtained with GRIS at GREGOR. A spectral-line inversion technique was used to infer the magnetic field vector and Doppler velocities from the full Stokes profiles. In total, three spectral lines were inverted and the variation of the magnetic properties was qualified using the average values of the radial circles. The sunspot is located close to the solar limb, and thus this allows us to make a geometrical determination of the height of the spectral line He I 1083 nm. We find the height of helium spectral line to be 970 km above the photospheric spectral lines directly from observation at a stable sunspot. The total magnetic field strength decreases with height over the sunspot; the rates are -0.34 G/km for the umbra and -0.28 G/km for the penumbra. The inclination increases with increasing height in the umbra, but decreases in the penumbra. In the umbra, the vertical component ($B_z$) decreases with height, while the horizontal component ($B_{hor}$) remains almost constant. In the penumbra this is reversed, as $B_z$ remains nearly constant over height, while $B_{hor}$ decreases. We also observe fast velocities with 30 km/s in small chromospheric patches on the central side of the spot. The key parameters depending on height in the sunspot are the $B_{z}$ component of the magnetic field for the umbra and the $B_{hor}$ component of the magnetic field for the penumbra.

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