Si x emission lines in spectra obtained with the Solar EUV Rocket Telescope and Spectrograph (SERTS)
Si x emission lines in spectra obtained with the Solar EUV Rocket Telescope and Spectrograph (SERTS)
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DOI：
10.1046/j.1365-8711.2000.03599.x
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发表时间：
2000-07
影响因子：
4.8
通讯作者：
F. Keenan;E. O'Shea;R. Thomas;J. Brosius;A. Katsiyannis;R. Ryans;R. Reid;A. Pradhan;H. L. Zhang
中科院分区：
文献类型：
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作者：
F. Keenan;E. O'Shea;R. Thomas;J. Brosius;A. Katsiyannis;R. Ryans;R. Reid;A. Pradhan;H. L. Zhang
给出了Six的2s22p、2s2p2和2p3能级跃迁的电子碰撞激发率的新的R矩阵计算方法。这些数据随后与最近对质子激发速率的估计结合使用，以得出涉及∼253-356A波长范围内跃迁的电子密度敏感发射线比理论。将这些结果与1989年太阳极紫外光火箭望远镜和光谱仪(SERTS)飞行期间对太阳活动区和次耀斑的观测结果进行了比较，结果表明，对于这两个太阳特征，由大多数Six线比率确定的电子密度彼此一致。此外，导出的密度也与由其他物种在与Six相似的电子温度下形成的诊断线估算的Ne值很好地吻合，如FexII和FeXIII。这些结果为本分析中采用的原子数据的总体精度提供了观测支持，因此也为线比计算提供了支持。然而，我们发现Six 256.32-A线在同一波长与He II跃迁混合，而292.25 A处的特征不是由于Six，但目前仍未确定。SERTS活动区光谱中253.81-A线的强度大约是理论预期的3倍，但原因尚不清楚，需要更多的观测来解释这种差异。
New R-matrix calculations of electron impact excitation rates for transitions among the 2s22p, 2s2p2 and 2p3 levels of Si x are presented. These data are subsequently used, in conjunction with recent estimates for proton excitation rates, to derive theoretical electron density sensitive emission-line ratios involving transitions in the ∼253–356 A wavelength range. A comparision of these with observations of a solar active region and subflare, obtained during the 1989 flight of the Solar EUV Rocket Telescope and Spectrograph (SERTS), reveals that the electron densities determined from most of the Si x line ratios are consistent with one another for both solar features. In addition, the derived densities are also in good agreement with the values of Ne estimated from diagnostic lines in other species formed at similar electron temperatures to Si x, such as Fe xii and Fe xiii. These results provide observational support for the general accuracy of the adopted atomic data, and hence line ratio calculations, employed in the present analysis. However, we find that the Si x 256.32-A line is blended with the He ii transition at the same wavelength, while the feature at 292.25 A is not due to Si x, but currently remains unidentified. The intensity of the 253.81-A line in the SERTS active region spectrum is about a factor of 3 larger than expected from theory, but the reason for this is unclear, and requires additional observations to explain the discrepancy.