| Abstract |
Due to computational requirements and numerical difficulties associated with coordinate singularity in spherical geometry, fully dynamic 3D magnetohydrodynamic (MHD) simulations of massive star winds are not readily available. Here we report results of the first such a 3D simulation using specific parameters representing the prototypical slowly rotating magnetic O star θ^1 Ori C, for which
centrifugal and other dynamical effects of rotation are negligible. The computed global structure in latitude and radius resembles that found in previous 2D simulations, with unimpeded outflow along open field lines near the magnetic poles, and a complex equatorial belt of inner wind trapping by closed loops near the stellar surface, giving way to outflow above the Alfven radius. In contrast to this previous 2D work, the 3D simulation described here now also shows how this complex structure fragments in azimuth, forming distinct clumps of closed loop infall within the Alfven radius. Applying these results in a 3D code for line radiative transfer, we show that emission from the associated 3D 'dynamical magnetosphere' matches well the observed Hα
emission seen from θ^1 Ori C, fitting both its dynamic
spectrum over rotational phase and the observed level of cycle-to-cycle stochastic variation. |