光学细线谱$κ$中非麦克斯韦分布的特征
Signatures of the non-Maxwellian $κ$-distributions in optically thin line spectra \subtitle{I. Theory and synthetic Fe IX--XIII spectra}
摘要：
我们调查的可能性诊断的程度偏离麦克斯韦分布使用单离子光谱起源于天体物理等离子体碰撞电离平衡。Fe IX-XIII激发的新原子数据是在电子能量κ分布的假设下积分的。探索了使用在任何波长处形成的单个离子的线的诊断方法。这种方法最大限度地减少了电离和复合速率的不确定性，以及可能存在的非平衡电离。碰撞强度的近似也进行了研究。大多数Fe IX-XIII EUV谱线的计算强度在恒定温度下与Kappa表现出一致的行为。这些品系的强度随着kappa而降低，其中绝大多数强品系的比率显示对kappa的敏感性很小或不敏感。几个线的比率，特别是涉及温度敏感的线，显示出对卡帕的灵敏度是百分之几十的顺序，或者，在Fe IX的情况下，高达两倍。在光谱的近紫外、可见光或红外部分的禁戒线是一个例外，其强度变化较小，甚至与kappa相反。最明显的例子是Fe X 6378 A红线，其强度随kappa增加而增加。这条线是偏离麦克斯韦分布的一个潜在的强指标。我们发现，它可以独立地进行密度诊断的κ，与许多铁XI-XIII线比显示出很强的密度敏感性和可忽略不计的敏感性κ和温度。我们还测试了碰撞强度的不同平均值。据发现，平均超过0.01的间隔在日志（E/Ryd）是足够的，以产生准确的分布平均碰撞强度在电离平衡的离子形成的温度。
英文摘要：
We investigate the possibility of diagnosing the degree of departure from the Maxwellian distribution using single-ion spectra originating in astrophysical plasmas in collisional ionization equilibrium. New atomic data for excitation of Fe IX-XIII are integrated under the assumption of a kappa-distribution of electron energies. Diagnostic methods using lines of a single ion formed at any wavelength are explored. Such methods minimize uncertainties from the ionization and recombination rates, as well as the possible presence of non-equilibrium ionization. Approximations to the collision strengths are also investigated. The calculated intensities of most of the Fe IX-XIII EUV lines show consistent behaviour with kappa at constant temperature. Intensities of these lines decrease with kappa, with the vast majority of ratios of strong lines showing little or no sensitivity to kappa. Several of the line ratios, especially involving temperature-sensitive lines, show a sensitivity to kappa that is of the order of several tens of per cent, or, in the case of Fe IX, up to a factor of two. Forbidden lines in the near-ultraviolet, visible, or infrared parts of the spectrum are an exception, with smaller intensity changes or even a reverse behaviour with kappa. The most conspicuous example is the Fe X 6378A red line, whose intensity incerases with kappa. This line is a potentially strong indicator of departures from the Maxwellian distribution. We find it possible to perform density diagnostics independently of kappa, with many Fe XI-XIII line ratios showing strong density-sensitivity and negligible sensitivity to kappa and temperature. We also tested different averaging of the collision strengths. It is found that averaging over 0.01 interval in log(E/Ryd) is sufficient to produce accurate distribution-averaged collision strengths at temperatures of the ion formation in ionization equilibrium.
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