Atomic input for modeling ionic mixtures in astrophysical plasma

Abstract Accurate atomic data are known as a key ingredient for modeling the physical behavior of a wide range of plasma throughout the universe. When these data are combined with simulations of ionic mixtures, they (may) help infer the temperature, electron density, and ionization state of the plasma under non-ideal plasma conditions. We here report about an expansion of JAC, the Jena Atomic Calculator, in order to encourage the modeling of ionic mixtures and their thermodynamic properties under different plasma conditions. Whereas emphasis has first been placed upon simulations of ionic compositions in (ideal) local thermodynamic equilibrium, various features are prepared in this code to account for non-ideal conditions, such as plasma screening contributions, the ionization potential depression (IPD) or some non-classical statistics. To demonstrate these features of JAC, we have calculated the mean charge and charge-state distribution of a hot carbon plasma as well as some ionic mixture from the sun’s photosphere at selected temperatures T and mass densities $$\rho _m$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>ρ</mml:mi> <mml:mi>m</mml:mi> </mml:msub> </mml:math> . These computations show a significant shift in the mean charge distribution, if the IPD is incorporated by means of a Stewart–Pyatt plasma model. Since the JAC toolbox is based on Dirac’s relativistic equation, the present expansion of the code will facilitate also the treatment of ionic mixtures with medium and heavy elements as relevant for neutron-star mergers and elsewhere.