KAPPA: A Package for the Synthesis of Optically Thin Spectra for the Non-Maxwellian κ-distributions. II. Major Update to Compatibility with CHIANTI Version 10

Abstract

KAPPA is a database and software for the calculation of the optically thin spectra for the non-Maxwellian κ-distributions that were recently diagnosed in the plasma of solar coronal loops, flares, as well as in the transition region. KAPPA is based on the widely used CHIANTI database and reproduces many of its capabilities for κ-distributions. Here we perform a major update of the KAPPA database, including a near-complete recalculation of the ionization, recombination, excitation, and deexcitation rates for all ions in the database, as well as an implementation of the two-ion model for calculations of relative-level populations (and intensities) if these are modified by ionization and recombination from or to excited levels. As an example of KAPPA usage, we explore novel diagnostics of κ, and show that O iii lines near 500 and 700 Å provide a strong sensitivity to κ, with some line intensity ratios changing by a factor of up to 2–4 compared to Maxwellian. This is much larger than previously employed diagnostics of κ.

Diagnostics of Non-Maxwellian Electron Distributions in Solar Active Regions from Fe xii Lines Observed by the Hinode Extreme Ultraviolet Imaging Spectrometer and Interface Region Imaging Spectrograph

“…For low κ = 2, the peak formation of the Fe XII 192.4 Å line occurs at higher T , and its intensity decreases. The shift in the temperature of the peak, as well as about half of the decrease of the peak, are due to the behaviour of the ionization equilibrium with κ Dzifčáková et al 2021). The decrease in excitation due to relatively-lower amount of electrons in the κ = 2 distribution at few hundred eV (top panel of Figure 10) also contributes to the decrease of the peak of the Fe XII 192.4 Å line.…”

“…To evaluate the effects of NMED, we considered the κdistributions, a well-known class of non-Maxwellian distributions characterized by a near-Maxwellian core and a power-law high-energy electron tail (see, e.g., Livadiotis 2017;Lazar & Fichtner 2021). We use the standard expression for κdistributions of the second kind (see the discussion in Dzifčáková et al 2021), namely…”

“…However, one line ratio sensitive to κ is not enough to determine the κ from observations. This is because the distribution function has two independent parameters, namely T and κ (Equation ( 5)), which thus need to be determined simultaneously (e.g., Dzifčáková & Kulinová 2010;Mackovjak et al 2013;Dudík et al , 2015Lörinčík et al 2020;Dzifčáková et al 2021). Therefore, it is advantageous to combine this ratio with a primarily temperature-sensitive Fe XII/Fe XIII ratio, which allows for decoupling of the sensitivities to κ and to T (see Figure 11) provided the plasma is in an ionization equilibrium.…”

“…To evaluate the effects of NMED, we considered the κ-distributions, a well known class of non-Maxwellian distributions characterized by a near-Maxwellian core and a power-law high-energy electron tail (see, e.g., Livadiotis 2017;Lazar & Fichtner in press). We use the standard expression for κ-distributions of the second kind (see the discussion in Dzifčáková et al 2021), namely where E is the electron kinetic energy, T is the temperature, k B is the Boltzmann constant, and A κ is a constant for normalization to unity. From the expression above it follows that the slope of the high-energy power-law slope of the high-energy tail of a κ-distribution is κ + 1/2.…”

“…The synthetic spectra for Fe XII and Fe XIII were obtained using the KAPPA database (Dzifčáková et al 2015(Dzifčáková et al , 2021, which allows for calculation of spectra for κ-distributions using the same atomic data as CHIANTI version 10 ( Dere et al 1997;Del Zanna et al 2021). We calculated the Fe XII and Fe XIII line intensities for a range of temperatures T and κ values and found that the EIS/IRIS ratio of Fe XII 192.4 Å / 1349 Å line intensities offer unprecedented sensitivity to NMED, with the difference between Maxwellian and κ = 2 being of about a factor of two, depending on temperature.…”