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A. ud-Doula, S. Owocki (Univ of Delaware, Bartol Research Institute)
We present fully dynamic numerical magnetohydrodynamic (MHD) simulations of line-driven winds from hot stars with assumed dipolar magnetic fields at the stellar surface. The magnetic fields can guide the wind outflows from higher latitudes towards the magnetic equator causing them to collide there with speeds of hundreds of km \, s-1. This may lead to significant equatorial density enhancements and wind shocks may heat up the gas to temperatures high enough to produce X-rays. Our results show that the governing parameter for how much the wind is influenced by the field is the `magnetic confinement wind number', \eta\ast ( = B2 R\ast2/{\dot M} v\infty), which characterizes the ratio between magnetic field energy density and kinetic energy density of the wind. We find that for \eta\ast of the order of unity or greater, magnetic fields can channel or confine the winds, and lead to significant spatial and temporal variability of wind properties. Such characteristics contrast with the classical view of steady and spherical stellar winds from hot stars, and indeed provide a potential model for the X-ray emission and UV wind line variability often detected from such massive stars.
The author(s) of this abstract have provided an email address for comments about the abstract: asif@udel.edu