Inference of electric currents in the solar photosphere
Inference of electric currents in the solar photosphere
复制标题
太阳光球层电流的推断
DOI：
10.1051/0004-6361/202142149
复制
发表时间：
2021
影响因子：
6.5
通讯作者：
Ruiz Cobo
中科院分区：
文献类型：
--
作者：
Pastor Yabar;Borrero;Quintero Noda;Ruiz Cobo
尽管它们很重要，但在太阳大气中对电流 j 进行常规和直接测量通常是不可能的。目的我们的目标是展示一种新开发的确定太阳光球层电流的方法的能力。方法我们采用三维辐射磁流体动力学 (MHD) 模拟来生成多条谱线的合成斯托克斯剖面，其空间分辨率相似 到新投入运行的 4 米丹尼尔 K. 井上太阳望远镜 (Daniel K. Inouye Solar Telescope) 太阳望远镜应达到的目标。我们应用新开发的具有磁流体静力 (MHS) 约束的偏振辐射传输方程的反演方法，从合成的斯托克斯剖面中推断出三维笛卡尔域 B(x,y,z) 中的磁场矢量。然后，我们应用安培定律从推断的磁场 B(x,y,z) 中确定电流 j，并将结果与原始 MHD 模拟中存在的电流进行比较。结果我们表明，这里采用的方法能够在电推断中获得合理的可靠性（接近 50% 的情况在两倍之内，对于 B≥ 300 G 的像素，这一点增加到 60%–70%）电流 对于低大气高度（光学深度为 500 nmτ5ε[1, 0.1]），无论反转的谱线数量是少量还是大量。在这些光球层之上，随着磁场变弱以及 MHS 近似变得不太准确，该方法的准确性会急剧下降。我们还发现，推断的电流具有与低磁化等离子体相关的下限值，其中磁场推断的不确定性阻碍了空间导数的足够准确的确定。结论我们提出了一种方法，允许从分光偏振观测推断深层大气层（光球层）的电流矢量的三个分量。
ContextDespite their importance, routine and direct measurements of electric currents,j, in the solar atmosphere have generally not been possible.AimsWe aim at demonstrating the capabilities of a newly developed method for determining electric currents in the solar photosphere.MethodsWe employ three-dimensional radiative magneto-hydrodynamic (MHD) simulations to produce synthetic Stokes profiles in several spectral lines with a spatial resolution similar to what the newly operational 4-meterDaniel K. InouyeSolar Telescope solar telescope should achieve. We apply a newly developed inversion method of the polarized radiative transfer equation with magneto-hydrostatic (MHS) constraints to infer the magnetic field vector in the three-dimensional Cartesian domain,B(x,y,z), from the synthetic Stokes profiles. We then apply Ampere’s law to determine the electric currents,j, from the inferred magnetic field,B(x,y,z), and compare the results with the electric currents present in the original MHD simulation.ResultsWe show that the method employed here is able to attain reasonable reliability (close to 50% of the cases are within a factor of two, and this increases to 60%–70% for pixels withB≥ 300 G) in the inference of electric currents for low atmospheric heights (optical depths at 500 nmτ5∈[1, 0.1]) regardless of whether a small or large number of spectral lines are inverted. Above these photospheric layers, the method’s accuracy strongly deteriorates as magnetic fields become weaker and as the MHS approximation becomes less accurate. We also find that the inferred electric currents have a floor value that is related to low-magnetized plasma, where the uncertainty in the magnetic field inference prevents a sufficiently accurate determination of the spatial derivatives.ConclusionsWe present a method that allows the inference of the three components of the electric current vector at deep atmospheric layers (photospheric layers) from spectropolarimetric observations.