An assessment of Fe xx-Fe xxii emission lines in SDO/EVE data as diagnostics for high-density solar flare plasmas using EUVE stellar observations
An assessment of Fe xx-Fe xxii emission lines in SDO/EVE data as diagnostics for high-density solar flare plasmas using EUVE stellar observations
复制标题
使用 EUVE 恒星观测对 SDO/EVE 数据中的 Fe xx-Fe xxii 发射线进行评估，作为高密度太阳耀斑等离子体的诊断
DOI：
10.1093/mnras/stx525
复制
发表时间：
2017
影响因子：
4.8
通讯作者：
Keenan F
中科院分区：
文献类型：
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作者：
Keenan F
太阳动力学观测站的极紫外线变率实验（EVE）获得了全圆盘太阳的极紫外线（EUV）光谱，光谱分辨率为100 μ m，节奏为10 s。由于混合，这种光谱分辨率通常被认为对于可靠地确定电子密度（Ne）敏感的发射线强度比来说太低。然而，先前的工作已经表明，在EVE的90-160 nm波长范围内，有限数量的Fexxi特征确实在相对较低的耀斑密度（Ne = 1011- 1012 cm −3）下提供了有用的Ne诊断。在这里，我们调查，如果额外的高度电离的Fe线比在EVE 90-160欧姆的范围内，可以可靠地采用作为氖诊断。特别是，这种诊断提供高Ne（~ 1013 cm-3）耀斑等离子体密度估计的潜力进行了评估。我们的研究采用EVE光谱的X级耀斑，结合观测的高度活跃的晚型恒星从theEUVE卫星加上实验数据诊断良好的托卡马克等离子体，这两者都是类似的波长覆盖范围和光谱分辨率的EVE。在EVE数据中确定了几个比率，这些比率产生了一致的电子密度值，包括Fexx 113.35/121.85和Fexxi 114.41/135.79，并相信它们作为EUVE和托卡马克结果提供的Ne诊断的可靠性。这些比值也允许测定太阳耀斑等离子体的密度，直到达到1013 cm −3。
The Extreme Ultraviolet Variability Experiment (EVE) on the Solar Dynamics Observatory obtains extreme-ultraviolet (EUV) spectra of the full-disc Sun at a spectral resolution of ∼1 Å and cadence of 10 s. Such a spectral resolution would normally be considered to be too low for the reliable determination of electron density (Ne) sensitive emission line intensity ratios, due to blending. However, previous work has shown that a limited number of Fexxifeatures in the 90–160 Å wavelength region of EVE do provide useful Ne-diagnostics at relatively low flare densities (Ne≃ 1011–1012cm−3). Here, we investigate if additional highly ionized Fe line ratios in the EVE 90–160 Å range may be reliably employed as Ne-diagnostics. In particular, the potential for such diagnostics to provide density estimates for high Ne(∼1013cm−3) flare plasmas is assessed. Our study employs EVE spectra for X-class flares, combined with observations of highly active late-type stars from theEUVEsatellite plus experimental data for well-diagnosed tokamak plasmas, both of which are similar in wavelength coverage and spectral resolution to those from EVE. Several ratios are identified in EVE data, which yield consistent values of electron density, including Fexx113.35/121.85 and Fexxii114.41/135.79, with confidence in their reliability as Ne-diagnostics provided by theEUVEand tokamak results. These ratios also allow the determination of density in solar flare plasmas up to values of ∼1013cm−3.