日冕中的氦线发射率
Helium line emissivities in the solar corona
摘要：
我们提出了新的碰撞辐射模型（CRM）的氦在静止的太阳日冕，并预测发射率的He和He $^+$线观察DKIST，太阳轨道器，和Proba-3。我们详细讨论了我们为这些模型选择的速率，突出了我们在以前的工作中发现的几个缺点。由于以前没有完整的和自洽的氦冠状CRM存在，我们已经基准我们最大的模型在密度为10 $^{6}$厘米$^{-3}$和温度为20,000 K对最近的标准物质开发的光电离星云。然后，我们提出了外太阳日冕的结果，使用新的双电子复合率，我们已经计算出，增加了约2倍的中性氦的丰度。我们还发现，所有的光学三重态He I线，特别是众所周知的He I 10830和5876 A线的强烈影响，从磁盘辐射的光激发和光电离，广泛的CRM模型需要获得正确的估计。在太阳附近，在电子密度为10 $^{8}$ cm $^{-3}$，温度为1 MK的条件下，我们预测He I 10830 A的发射率与强Fe XIII日冕线10798 A的发射率相当。然而，我们预计，相对于Fe XIII，He I的发射率在外日冕中会急剧下降。我们确认，他$^+$莱曼$α$在304 A也显着受光激发，预计将被检测到一个强大的日冕线几个太阳半径。
英文摘要：
We present new collisional-radiative models (CRMs) for helium in the quiescent solar corona, and predict the emissivities of the He and He$^+$ lines to be observed by DKIST, Solar Orbiter, and Proba-3. We discuss in detail the rates we selected for these models, highlighting several shortcomings we have found in previous work. As no previous complete and self-consistent coronal CRM for helium existed, we have benchmarked our largest model at a density of 10$^{6}$ cm$^{-3}$ and temperature of 20,000 K against recent CRMs developed for photoionised nebulae. We then present results for the outer solar corona, using new dielectronic recombination rates we have calculated, which increase the abundance of neutral helium by about a factor of two. We also find that all the optical triplet He I lines, and in particular the well known He I 10830 and 5876 A lines are strongly affected by both photo-excitation and photo-ionisation from the disk radiation, and that extensive CRM models are required to obtain correct estimates. Close to the Sun, at an electron density of 10$^{8}$ cm$^{-3}$ and temperature of 1 MK, we predict the emissivity of the He I 10830 A to be comparable to that of the strong Fe XIII coronal line at 10798 A. However, we expect the He I emissivity to sharply fall in the outer corona, with respect to Fe XIII. We confirm that the He$^+$ Lyman $α$ at 304 A is also significantly affected by photo-excitation and is expected to be detectable as a strong coronal line up to several solar radii.
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