Observations of the Quiet Sun during the Deepest Solar Minimum of the Past Century with Chandrayaan-2 XSM: Elemental Abundances in the Quiescent Corona
Observations of the Quiet Sun during the Deepest Solar Minimum of the Past Century with Chandrayaan-2 XSM: Elemental Abundances in the Quiescent Corona
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使用 Chandrayaan-2 XSM 观测上个世纪最深太阳极小期期间的安静太阳：静止日冕中的元素丰度
DOI：
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发表时间：
2021
影响因子：
7.9
通讯作者：
Sushil Kumar
中科院分区：
文献类型：
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作者：
S. Vadawale;B. Mondal;N. Mithun;A. Sarkar;P. Janardhan;B. Joshi;A. Bhardwaj;M. Shanmugam;A. Patel;Hitesh Kumar L. Adalja;S. K. Goyal;T. Ladiya;N. K. Tiwari;Nishant Singh;Sushil Kumar
已知具有低第一电离势(FIP)的元素在日冕活动区环中的丰度是光球层的3-4倍。有观测表明，这种观测到的“FIP偏差”在日冕的其他部分可能是不同的，因此这种观测对于理解潜在的机制很重要。月船2号任务上的太阳X射线监视器(XSM)在2019-2020年太阳极小期期间以软X射线的形式对太阳进行了光谱观测，这被认为是过去一个世纪最安静的太阳极小期。这些观测为在没有任何活动区的情况下研究静止日冕的软X射线光谱提供了一个独特的机会。通过模拟来自XSM的高分辨率宽带X射线光谱，我们估计了可能是太阳X射线强度最低时期的温度和辐射测量。我们发现，当温度在2mK左右时，得到的参数随时间几乎保持不变，这表明发射是由X射线亮点主导的。我们还得到了Mg、Al和Si相对于H的丰度，发现FIP偏置为∼2，低于活动区的观测值。
Elements with low first ionization potential (FIP) are known to be 3–4 times more abundant in active region loops of the solar corona than in the photosphere. There have been observations suggesting that this observed “FIP bias” may be different in other parts of the solar corona and such observations are thus important in understanding the underlying mechanism. The Solar X-ray Monitor (XSM) on board the Chandrayaan-2 mission carried out spectroscopic observations of the Sun in soft X-rays during the 2019–2020 solar minimum, considered to be the quietest solar minimum of the past century. These observations provided a unique opportunity to study soft X-ray spectra of the quiescent solar corona in the absence of any active regions. By modeling high-resolution broadband X-ray spectra from XSM, we estimate the temperature and emission measure during periods of possibly the lowest solar X-ray intensity. We find that the derived parameters remain nearly constant over time with a temperature around 2 MK, suggesting the emission is dominated by X-ray bright points. We also obtain the abundances of Mg, Al, and Si relative to H, and find that the FIP bias is ∼2, lower than the values observed in active regions.
影响因子：
6.5
作者：
G. Del Zanna
通讯作者：
G. Del Zanna