Stellar Winds, Magnetic Fields and Disks

Abstract

All main sequence stars lose mass via stellar winds. The winds of cool stars like the sun are driven by gas pressure gradient. However, the winds of hot massive stars which tend to be luminous are driven by emitted by the star radiation pressure. Mass loss from such winds are significantly higher. In this article, I describe the nature of such radiatively driven winds and show how they interact with rotation and magnetic fields leading to stellar spindown and large-scale disk-like structures. In particular, I show that the overall degree to which the wind is influenced by the field depends largely on a single, dimensionless, “wind magnetic confinement parameter”, η _∗ $({=} B_{\mathrm{eq}}^{2} R_{\ast}^{2}/{\dot{M}} v_{\infty})$, which characterizes the ratio between magnetic field energy density and kinetic energy density of the wind.