PopRatio: A program to calculate atomic level populations in astrophysical plasmas

PopRatio: A program to calculate atomic level populations in astrophysical plasmas

We describe a Fortran 90 program to calculate population ratios of atomic levels. The program solves the equations of statistical equilibrium considering all possible bound-bound processes: spontaneous, collisional or radiation induced (the later either directly or by fluorescence). There is no limit on the number of levels or in the number of processes that may be taken into account. The progr...

Understanding the time dependence of atomic level populations in evolving plasmas

The time dependence of atomic level populations in evolving plasmas is studied using an eigenfunction expansion of the non-LTE rate equations. The work aims to develop understanding without the need for, and as an aid to, numerical solutions. The discussion is mostly limited to linear systems, especially those for optically thin plasmas, but the implicitly non-linear case of non-LTE radiative t...

ElecSus: A program to calculate the electric susceptibility of an atomic ensemble

We present a computer program and underlying model to calculate the electric susceptibility of a gas, which is essential to predict its absorptive and dispersive properties. Our program focuses on alkali-metal vapours where we use a matrix representation of the atomic Hamiltonian in the completely uncoupled basis in order to calculate transition frequencies and strengths. The program calculates...

Hydrodynamics, magnetohydrodynamics, and astrophysical plasmas

1 Introduction It is not uncommon to encounter the assertion that the dynamical evolution of the large-scale bulk velocity v of a collisionless gas is not described by the hydrodynamic (HD) equations. A favorite " reason " is the statement that pressure cannot be defined in the absence of collisions. Then in some quarters it is believed that the large-scale bulk dynamics of a swirling magnetize...

Nuclear Excitation Processes in Astrophysical Plasmas