Diagnosing transient ionization in dynamic events
Diagnosing transient ionization in dynamic events
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DOI：
10.1051/0004-6361/201321902
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发表时间：
2013-07
影响因子：
6.5
通讯作者：
J. Doyle;A. Giunta;M. Madjarska;H. Summers;M. O’Mullane;A. Singh
中科院分区：
文献类型：
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作者：
J. Doyle;A. Giunta;M. Madjarska;H. Summers;M. O’Mullane;A. Singh
目标。本研究的目的是提供一个诊断线比，这将使观察者，以确定是否等离子体是在一个瞬态电离状态。方法.我们使用原子数据和分析结构（ADAS）计算线贡献函数的两条线，Si iv 1394 A和O iv 1401 A，形成于太阳过渡区。采用广义碰撞辐射理论。它包括所有的辐射和电子碰撞过程，除了光子引起的过程。状态分辨的直接电离和重组，并从下一个电离阶段也被考虑在内。结果对于具有几秒的衰减时间的动态突发，Si iv 1394 A线可以在第一秒的分数中增强2-4倍，其中线贡献函数中的峰值最初发生在由于与电离平衡条件相比的瞬态电离而导致的更高的电子温度。另一方面，Oiv 1401 A没有显示出这样的任何增强。因此，这两条线的比例，这可以观察到的界面区成像光谱仪，可以用来作为一个诊断的瞬态电离。结论.我们表明，同时高节奏的观测太阳过渡区形成的两条线可以作为一个直接的诊断所观察到的等离子体是否在瞬态电离。这两条谱线的比率可以在几秒钟内改变四倍，这仅仅是由于瞬时电离。
Aims. The present study aims to provide a diagnostic line ratio that will enable the observer to determine whether a plasma is in a state of transient ionization. Methods. We use the Atomic Data and Analysis Structure (ADAS) to calculate line contribution functions for two lines, Si iv 1394 A and O iv 1401 A, formed in the solar transition region. The generalized collisional-radiative theory is used. It includes all radiative and electron collisional processes, except for photon-induced processes. State-resolved direct ionization and recombination to and from the next ionization stage are also taken into account. Results. For dynamic bursts with a decay time of a few seconds, the Si iv 1394 A line can be enhanced by a factor of 2–4 in the first fraction of a second with the peak in the line contribution function occurring initially at a higher electron temperature due to transient ionization compared to ionization equilibrium conditions. On the other hand, the O iv 1401 A does not show such any enhancement. Thus the ratio of these two lines, which can be observed with the Interface Region Imaging Spectrograph, can be used as a diagnostic of transient ionization. Conclusions. We show that simultaneous high-cadence observations of two lines formed in the solar transition region may be used as a direct diagnostic of whether the observed plasma is in transient ionization. The ratio of these two lines can change by a factor of four in a few seconds owing to transient ionization alone.