KAPPA: A Package for Synthesis of optically thin spectra for the non-Maxwellian kappa-distributions based on the CHIANTI database

TL;DR

The paper introduces KAPPA, a software package that synthesizes optically thin spectra for non-Maxwellian kappa-distributions using the CHIANTI database, aiding astrophysical plasma diagnostics.

Contribution

KAPPA provides a new tool for modeling spectra with kappa-distributions, including ionization, recombination, and excitation data, with validated approximate methods for collision strengths.

Findings

Achieves better than 5% accuracy in collision strength calculations

Provides synthetic spectra and AIA response examples

Enables plasma diagnostics with non-Maxwellian distributions

Abstract

The non-Maxwellian $\kappa$-distributions have been detected in the solar transition region and flares. These distributions are characterized by a high-energy tail and a near-Maxwellian core and are known to have significant impact on the resulting optically thin spectra arising from collisionally dominated astrophysical plasmas. We developed the KAPPA package (http://kappa.asu.cas.cz) for synthesis of such line and continuum spectra. The package is based on the freely available CHIANTI database and software, and can be used in a similar manner. Ionization and recombination rates together with the ionization equilibria are provided for a range of $\kappa$ values. Distribution-averaged collision strengths for excitation are obtained by an approximate method for all transitions in all ions available within CHIANTI. The validity of this approximate method is tested by comparison with direct calculations. Typical precisions of better than 5% are found, with all cases being within 10%. Tools for calculation of synthetic line and continuum intensities are provided and described. Examples of the synthetic spectra and SDO/AIA responses to emission for the $\kappa$-distributions are given.