Abstract

Contributed Talk - Splinter Computational

Thursday, 12 September 2024, 14:45   (S26)

A non-equilibrium multi-ion solver for ionized plasmas

Arun Mathew, Jonathan Mackey
Dublin Institute for Advanced Studies

While many astrophysical plasmas can be modelled successfully assuming ionization and thermal equilibrium, in some cases this is not appropriate and a non-equilibrium approach is required. In nebulae around evolved stars the local elemental abundances may also strongly vary in space and time. Here we present a non-equilibrium multi-ion module developed for the fluid-dynamics code PION, including collisional and photo-reactions, and ion-by-ion radiative cooling. The chemical kinetics solver allows time- and space-dependent elemental abundances and evolves the ionization state of the elements H, He, C, N, O, Ne, Si, S and Fe (up to 99 species). Element and ion mass fractions are advected using passive scalars. The module is validated by comparing with equilibrium and non-equilibrium calculations in the literature. The time-dependent expansion of a Wolf-Rayet nebula is studied, including photoionization and collisional processes. The multi-ion module allows prediction of spectral line luminosity and maps in cases where the plasma is out of ionization equilibrium. Based on current performance, 1D and 2D simulations are feasible with moderate computing resources, with 3D possible on large supercomputers.