Accretion-powered Stellar Winds. II. Numerical Solutions for Stellar Wind Torques

摘要: In order to explain the slow rotation observed in a large fraction of accreting pre-main-sequence stars (CTTSs), we explore role stellar winds torquing down stars. For this mechanism be effective, need have relatively high outflow rates, and thus would likely powered by accretion process itself. Here, use numerical magnetohydrodynamical simulations compute detailed two-dimensional (axisymmetric) wind solutions, determine spin-down torque on star. We discuss driving mechanisms then adopt Parker-like (thermal pressure driven) wind, modified rotation, magnetic fields, enhanced mass-loss rate (relative Sun). range parameters relevant for CTTSs, including variations mass, radius, spin rate, surface field strength, acceleration rate. also consider both dipole quadrupole geometries. Our indicate that is sufficient magnitude important spinning "typical" CTTS, ~10−9 M☉ yr−1. The are wide-angle, self-collimated flows, as expected rotator with moderately fast rotation. cases quadrupolar produce much weaker than same demonstrating geometry plays fundamental determining torque. Cases varying show smaller torque, suggesting details less important. our computed results fit semianalytic formula effective Alfven radius well This allows considerable predictive power, an improvement over existing approximations.