Dynamic Evolution of a Quasi-Spherical General Polytropic Magnetofluid with Self-Gravity

TL;DR

This paper investigates the self-similar evolution of a quasi-spherical, magnetized polytropic gas under self-gravity, generalizing previous models by relaxing certain constraints and exploring complex MHD behaviors and solutions.

Contribution

It introduces a more general self-similar MHD model for polytropic gases, removing previous constraints and analyzing a wider range of behaviors and solutions.

Findings

Analysis of magnetosonic critical curves

Construction of global semi-complete MHD solutions

Identification of astrophysical applications

Abstract

In various astrophysical contexts, we analyze self-similar behaviours of magnetohydrodynamic (MHD) evolution of a quasi-spherical polytropic magnetized gas under self-gravity with the specific entropy conserved along streamlines. In particular, this MHD model analysis frees the scaling parameter $n$ in the conventional polytropic self-similar transformation from the constraint of $n+\gamma=2$ with $\gamma$ being the polytropic index and therefore substantially generalizes earlier analysis results on polytropic gas dynamics that has a constant specific entropy everywhere in space at all time. On the basis of the self-similar nonlinear MHD ordinary differential equations, we examine behaviours of the magnetosonic critical curves, the MHD shock conditions, and various asymptotic solutions. We then construct global semi-complete self-similar MHD solutions using a combination of analytical and numerical means and indicate plausible astrophysical applications of these magnetized flow solutions with or without MHD shocks.