The EUV spectrum of the Sun: SOHO, SEM, and CDS irradiances
The EUV spectrum of the Sun: SOHO, SEM, and CDS irradiances
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太阳的 EUV 光谱：SOHO、SEM 和 CDS 辐照度
DOI：
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
L. Didkovsky
中科院分区：
文献类型：
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作者：
G. Zanna;S. Wieman;V. Andretta;L. Didkovsky
我们使用校准的极端紫外（EUV）光谱辐照度与太阳和日光层天文台（SOHO）的日冕诊断光谱仪正常入射光谱仪（NIS）的观测获得的太阳EUV监视器（SEM）的一阶带，260至340（SEM 1）估计测量的信号。NIS直接以二阶观测谐振线He ii 304 A和Sixi 303 A。波段中其他谱线的辐照度是用差分发射测量（DEM）建模，使用更新的原子数据来估计的。这里分析的观测是在1998-2011年期间获得的，这意味着它们跨越了第23周期的最大值和最小值。SEM 1降解的现有知识用于在NIS观察期间找到有效区域，并预测整个带的SEM 1计数率。总计数率，估计折叠的NIS为基础的光谱与SEM 1的有效面积，同意非常好（10-20%）与观察到的太阳活动极小期条件下，当He ii 304 A是占主导地位的贡献带。与太阳动力学天文台（SDO）的极紫外变率实验（EVE）观测结果也有很好的一致性，另一方面，在第23周极大值期间，预测的SEM 1计数率明显低于观测值（约30%）。在最大条件下，SEM 1波段的太阳光谱发生显著变化，其中He ii 304 A仅贡献约40%。观测到的计数率的一个重要部分来自最近发现的带外光谱区域的日冕发射。对这种差异的解释需要进一步调查。
We use calibrated extreme-UV (EUV) spectral irradiances obtained from observations with the Solar & Heliospheric Observatory (SOHO) Coronal Diagnostics Spectrometer Normal Incidence Spectrometer (NIS) to estimate the signal measured by the Solar EUV Monitor (SEM) first-order band, 260 to 340 A (SEM 1). The NIS observes the resonance lines He ii 304 A and Sixi 303 A directly in second order. The irradiances of the other lines in the band are estimated with a differential emission measure (DEM) modelling, using updated atomic data. The observations analysed here were obtained during 1998–2011, which means that they span the maximum and minimum of Cycle 23. The current knowledge of the SEM 1 degradation is used to find effective areas during the dates of the NIS observations and to predict the SEM 1 count rates across the band. The total count rates, estimated by folding the NIS-based spectra with the SEM 1 effective areas, agree very well (within 10–20%) with the observed ones during solar minimum conditions, when the He ii 304 A is the dominant contribution to the band. Excellent agreement with the Solar Dynamics Observatory (SDO) Extreme ultraviolet Variability Experiment (EVE) observations is also found. On the other hand, the predicted SEM 1 count rates during the Cycle-23 maximum are significantly (by about 30%) lower than the observed ones. The solar spectrum in the SEM 1 band changes significantly during maximum conditions, with the He ii 304 A only contributing about 40%. A significant fraction of the observed count rates comes from coronal emission in an off-band spectral region that has recently been discovered. An explanation for the discrepancy needs further investigation.
太阳的 EUV 光谱：太阳周期期间的 SOHO CDS NIS 辐射率 23
影响因子：
6.5
作者：
Andretta V
通讯作者：
Andretta V