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arXiv 2201.07290astro-ph.SR
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用IRIS Si IV研究非热速度的中心-边缘变化

The Center-to-Limb Variation of Non-Thermal Velocities using IRIS Si IV

Yamini K. Rao, Giulio Del Zanna, Helen E. Mason

摘要:

我们研究的非热的速度在安静的太阳使用各种高空间,时间和光谱分辨率的观测接口区域成像光谱仪(IRIS)。我们将我们的分析集中在过渡区使用的光学细线(Si IV 1393.7),并选择线的轮廓,接近高斯。我们发现证据的中心到肢体的变化,使用不同的观察具有不同的曝光时间,范围从5-30秒。观测到临边附近的非热速度分布在20 km/s $^{-1}$附近达到峰值,而圆盘观测则在15 km/s $^{-1}$附近达到峰值。分布也不同。如前所述,非热速度的总体变化与线的强度相关。盘上的速度小于大多数以前的观测。在一般情况下,我们发现,非热速度是独立的选定的曝光时间。Si IV线似乎没有表现出任何显著的不透明效果。我们的结论是,这些多普勒运动主要是横向的径向方向。从这些IRIS观测中验证了摇摆/扭转运动导致这种变化的可能性。

英文摘要:

We study the non-thermal velocities in the quiet-sun using various high spatial, temporal, and spectral resolution observations from the Interface Region Imaging Spectrograph (IRIS). We focus our analysis on the transition region using the optically thin line (Si IV 1393.7 Å), and select line profiles that are nearly Gaussian. We find evidence of a centre-to-limb variation using different observations having different exposure times, ranging from 5-30 s. The distribution of non-thermal velocities close to the limb are observed to peak around 20 km s$^{-1}$ while the disc observations show a peak around 15 km s$^{-1}$. The distributions are also different. The overall variation in the non-thermal velocities are correlated with the intensity of the line, as found previously. The on-disc velocities are smaller than most previous observations. In general, we find that the non-thermal velocities are independent of the selected exposure times. The Si IV lines didn't seem to exhibit any significant opacity effects. We conclude that these Doppler motions are mostly transverse to the radial direction. The possibility of swaying/torsional motions leading to such variations are validated from these IRIS observations.

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