Straight outta photosphere: Open solar flux without coronal modeling,Astronomy & Astrophysics

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Straight outta photosphere: Open solar flux without coronal modeling
Astronomy & Astrophysics ( IF 5.4 ) Pub Date : 2024-08-22 , DOI: 10.1051/0004-6361/202451267
Ismo Tähtinen , Timo Asikainen , Kalevi Mursula

Context. The open solar flux, that is, the total magnetic flux escaping the Sun, is one of the most important parameters connecting solar activity to the Earth. The open solar flux is commonly estimated from photospheric magnetic field measurements by making model assumptions about the solar corona. However, the question in which way the open solar flux is directly related to the distribution of the photospheric magnetic field is still partly unknown.Aims. We aim to reconstruct the open solar flux directly from the photospheric magnetic fields without making any assumptions about the corona and without using coronal hole observations, for instance.Methods. We modified an earlier vector sum method by taking magnetic field polarities into account and applied the method to the synoptic magnetograms of six instruments to determine the open solar flux from solar cycles 21–24.Results. The modified vector sum method produces a vector of the global solar magnetic field whose magnitude closely matches the open solar flux from the potential field source surface (PFSS) model both by the absolute scale and the overall time evolution for each of the six magnetograms. The latitude of this vector follows the Hale cycle by always pointing toward the dominantly positive-polarity hemisphere, and its longitude coincides with the location of the main coronal holes of the McIntosh Archive. We find multi-year periods during which the longitude of the vector slowly drifts or stays rather stationary in the Carrington frame. These periods are punctuated by times when the longitude moves rapidly in the Carrington frame. By comparing the magnitude of this vector to the open solar flux calculated from the PFSS model with different source surface heights, we find that the best match is produced with a source surface height R_{ss_{= 2.4 − 2.5 R_{⊙_.}}}

中文翻译：

直接脱离光球层：无需日冕建模即可开放太阳通量

语境。开放太阳通量，即逃离太阳的总磁通量，是连接太阳活动与地球的最重要参数之一。开放太阳通量通常是通过对日冕进行模型假设，根据光球磁场测量来估计的。然而，开放太阳通量以何种方式与光球磁场分布直接相关的问题仍然部分未知。例如，我们的目标是直接从光球磁场重建开放太阳通量，而不对日冕做出任何假设，也不使用日冕洞观测。我们通过考虑磁场极性来修改早期的矢量和方法，并将该方法应用于六台仪器的天气磁图，以确定太阳周期 21-24 的开放太阳通量。结果。改进的矢量和方法产生了一个全球太阳磁场矢量，其大小与来自势场源表面（PFSS）模型的开放太阳通量密切匹配，无论是绝对尺度还是六个磁力图中每一个的总体时间演化。该矢量的纬度遵循海尔周期，始终指向占主导地位的正极性半球，其经度与麦金托什档案馆主要日冕洞的位置一致。我们发现在卡林顿坐标系中，矢量的经度在多年期间缓慢漂移或保持相当静止。这些周期被卡林顿坐标系中经度快速移动的时间所打断。通过将该矢量的大小与不同源表面高度的 PFSS 模型计算出的开放太阳通量进行比较，我们发现源表面高度 Rss = 2.4 − 2.5 R⊙ 产生最佳匹配。

更新日期：2024-08-23

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