Numerical simulations of stellar winds: polytropic models

TL;DR

This paper presents numerical simulations of stellar winds using polytropic models, extending from simple spherically symmetric cases to complex axisymmetric, magnetized, rotating outflows, demonstrating the versatility of the Versatile Advection Code.

Contribution

It introduces a comprehensive numerical approach to model steady-state stellar winds, including magnetic and rotational effects, generalizing analytical solutions to 2D axisymmetric configurations.

Findings

Successful simulation of axisymmetric, magnetized stellar winds

Validation of numerical solutions using flux functions

Modeling of both wind and dead zones in stellar outflows

Abstract

We discuss steady-state transonic outflows obtained by direct numerical solution of the hydrodynamic and magnetohydrodynamic equations. We make use of the Versatile Advection Code, a software package for solving systems of (hyperbolic) partial differential equations. We proceed stepwise from a spherically symmetric, isothermal, unmagnetized, non-rotating Parker wind to arrive at axisymmetric, polytropic, magnetized, rotating models. These represent 2D generalisations of the analytical 1D Weber-Davis wind solution, which we obtain in the process. Axisymmetric wind solutions containing both a `wind' and a `dead' zone are presented. Since we are solving for steady-state solutions, we efficiently exploit fully implicit time stepping. The method allows us to model thermally and/or magneto-centrifugally driven stellar outflows. We particularly emphasize the boundary conditions imposed at the stellar surface. For these axisymmetric, steady-state solutions, we can use the knowledge of the flux functions to verify the physical correctness of the numerical solutions.