The EUV helium spectrum in the quiet Sun: A by-product of coronal emission?
The EUV helium spectrum in the quiet Sun: A by-product of coronal emission?
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安静太阳中的 EUV 氦光谱：日冕发射的副产品？
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
S. Jordan
中科院分区：
文献类型：
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作者：
V. Andretta;G. Zanna;S. Jordan
在本文中，我们测试的机制之一，提出了解释太阳氦光谱的强度和其他观测到的属性，特别是其极紫外（EUV）共振线。所谓的光电离-电离（P-R）机制涉及氦原子和离子通过EUV日冕辐射的光电离，随后是复合级联。我们提出了校准测量的EUV通量获得的两个CDS光谱仪在SOHO上，在静止的太阳能区域。我们能够获得一个基本上完整的估计的总光电离通量在波长范围低于504（光电离阈值为黑），以及同时测量与最强的EUV黑和黑线的强度相同的仪器：黑584，黑537，和黑304。我们发现，没有足够的EUV电离光子来解释所观察到的氦线强度。更具体地说，我们得出结论，Heii强度不能单独用P-R机制来解释。然而，我们的研究结果，留下了开放的可能性，即He i光谱可以形成的P-R机制，与Heii 304线作为一个重要的光电离源。
In this paper we test one of the mechanisms proposed to explain the intensities and other observed properties of the solar helium spectrum, and in particular of its Extreme-Ultraviolet (EUV) resonance lines. The so-called Photoionisation- Recombination (P-R) mechanism involves photoionisation of helium atoms and ions by EUV coronal radiation, followed by recombination cascades. We present calibrated measurements of EUV flux obtained with the two CDS spectrometers on board SOHO, in quiescent solar regions. We were able to obtain an essentially complete estimate of the total photoionising flux in the wavelength range below 504 A (the photoionisation threshold for Hei), as well as simultaneous measurements with the same instruments of the intensities of the strongest EUV Hei and Heii lines: Hei584, Hei537, and Heii304. We find that there are not enough EUV ionising photons to account for the observed helium line intensities. More specifically, we conclude that Heii intensities cannot be explained by the P-R mechanism alone. Our results, however, leave open the possibility that the He i spectrum could be formed by the P-R mechanism, with the Heii304 line as a significant photoionisating source.