arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1702.06018astro-ph.SR
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来自太阳大气II三维模型的毫米辐射。色球磁场

Millimeter radiation from a 3D model of the solar atmosphere II. Chromospheric magnetic field

Maria Loukitcheva, Stephen M. White, Sami K. Solanki, Gregory D. Fleishman, Mats Carlsson

摘要:

我们使用国家的最先进的,三维的非本地热力学平衡(非LTE)辐射磁流体动力学模拟安静的太阳大气进行详细的测试色球磁场诊断从自由的辐射在毫米和亚毫米波长(mm/submm)。由毫米/亚毫米亮度谱和毫米频率下合成的圆偏振度推导出磁场的垂直分量。我们使用阿塔卡马大型毫米/亚毫米阵列(ALMA)观测到的频段作为方便的参考。所得到的磁场图描述了太阳色球层中相关波长的有效形成高度处的纵向磁场。在模型和当前观测的空间分辨率下,推导的和模型色球磁场的比较显示出良好的相关性,但有低估模型场的趋势。大约10%的系统差异可能是由于在对辐射有贡献的高度上恢复的场的平均值,由贡献的强度加权。总的来说,用毫米/亚毫米波段的自由-自由辐射探测磁场纵向分量的方法是适用于测量弱静太阳磁场的。然而,成功地利用这一技术需要非常精确地测量天线的极化特性(初级波束和接收器极化响应),这将是决定色球磁场可测量水平的主要因素。因此,毫米波圆偏振辐射的高分辨率和高精度观测可以成为产生色球纵向磁图的有力工具。

英文摘要:

We use state-of-the-art, three-dimensional non-local thermodynamic equilibrium (non-LTE) radiative magnetohydrodynamic simulations of the quiet solar atmosphere to carry out detailed tests of chromospheric magnetic field diagnostics from free-free radiation at millimeter and submillimeter wavelengths (mm/submm). The vertical component of the magnetic field was deduced from the mm/submm brightness spectra and the degree of circular polarization synthesized at millimeter frequencies. We used the frequency bands observed by the Atacama Large Millimeter/Submillimeter Array (ALMA) as a convenient reference. The magnetic field maps obtained describe the longitudinal magnetic field at the effective formation heights of the relevant wavelengths in the solar chromosphere. The comparison of the deduced and model chromospheric magnetic fields at the spatial resolution of both the model and current observations demonstrates a good correlation, but has a tendency to underestimate the model field. The systematic discrepancy of about 10 percent is probably due to averaging of the restored field over the heights contributing to the radiation, weighted by the strength of the contribution. On the whole, the method of probing the longitudinal component of the magnetic field with free-free emission at mm/submm wavelengths is found to be applicable to measurements of the weak quiet-Sun magnetic fields. However, successful exploitation of this technique requires very accurate measurements of the polarization properties (primary beam and receiver polarization response) of the antennas, which will be the principal factor that determines the level to which chromospheric magnetic fields can be measured. Consequently, high-resolution and high-precision observations of circularly polarized radiation at millimeter wavelengths can be a powerful tool for producing chromospheric longitudinal magnetograms.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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