PION: simulations of nebulae around stars

PION is a grid-based fluid dynamics code for hydrodynamics and magnetohydrodynamics, including a ray-tracing module for calculating the attenuation of radiation from point sources of ionizing photons. It also has a module for coupling fluid dynamics and the radiation field to microphysical processes such as heating/cooling and ionization/recombination. The algorithms are described in Mackey et al. (2021), Mackey (2012), Mackey & Lim (2011), Mackey & Lim (2010), and with more recent updates in.

PION was written to model the evolution of HII regions, photoionized bubbles that form around hot stars, and developed to include stellar wind sources so that both wind bubbles and photoionized bubbles can be simulated at the same time. It is versatile enough to be extended to other applications.

The current version of PION is 2.0.0, available at the release page.