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arXiv 1910.12964astro-ph.SR
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缓慢变化的日冕。II。F $_{10.7}$的组成及其在EUV代理中的应用

The Slowly Varying Corona. II. The Components of F $_{10.7}$ and Their Use in EUV Proxies

S. J. Schonfeld, S. M. White, C. J. Henney, R. A. Hock-Mysliwiec, R. T. J. McAteer

备注：
11 pages, 10 figures
发表信息：
ApJ 884:141 2019
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摘要：

使用Schonfeld等人（2017）计算的四年全圆盘积分日冕差分发射测量，我们研究了韧致辐射和陀螺共振发射在F $_{10.7}$观测中的相对贡献，10.7 cm（2.8 GHz）太阳微波光谱通量密度和常用的活动代理。我们确定，大多数的日冕F $_{10.7}$产生的韧致辐射机制，但在个别太阳旋转观察到的变化往往是由旋转的磁盘陀螺共振源驱动。我们的分析表明，色球层可能有助于显着F $_{10.7}$的变化和日冕韧致辐射占14.2 $\pm$ 2.1 sfu（$\sim20\%$）的观测到的太阳最低水平。在高活性水平下，韧致辐射发射与总F $_{10.7}$具有幂律关系，并且这与低活性期间观察到的线性相结合，产生作为F $_{10.7}$的函数的韧致辐射分量的连续可微分分段拟合。我们发现，韧致辐射组件配合，以及镁II指数，更好地与所观察到的5-37 nm光谱比常见的81天平均F $_{10.7}$代理。Henney等人（2012年）的中等强度光球磁场参数化也很好地近似了F $_{10.7}$的韧致辐射分量，这表明它可以预测用于大气研究和业务模型。

英文摘要：

Using four years of full-disk-integrated coronal differential emission measures calculated in Schonfeld et al. (2017), we investigate the relative contribution of bremsstrahlung and gyroresonance emission in observations of F$_{10.7}$, the 10.7 cm (2.8 GHz) solar microwave spectral flux density and commonly used activity proxy. We determine that the majority of coronal F$_{10.7}$ is produced by the bremsstrahlung mechanism, but the variability observed over individual solar rotations is often driven by gyroresonance sources rotating across the disk. Our analysis suggests that the chromosphere may contribute significantly to F$_{10.7}$ variability and that coronal bremsstrahlung emission accounts for 14.2 $\pm$ 2.1 sfu ($\sim20\%$) of the observed solar minimum level. The bremsstrahlung emission has a power-law relationship to the total F$_{10.7}$ at high activity levels, and this combined with the observed linearity during low activity yields a continuously differentiable piecewise fit for the bremsstrahlung component as a function of F$_{10.7}$. We find that the bremsstrahlung component fit, along with the Mg II index, correlates better with the observed 5-37 nm spectrum than the common 81 day averaged F$_{10.7}$ proxy. The bremsstrahlung component of F$_{10.7}$ is also well approximated by the moderate-strength photospheric magnetic field parameterization from Henney et al. (2012), suggesting that it could be forecast for use in both atmospheric research and operational models.

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