Turbulence-driven Polar Winds from T Tauri Stars Energized by Magnetospheric Accretion - AstrophysicsReport as inadecuate

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Abstract: Pre-main-sequence stars are observed to be surrounded by both accretion flowsand some kind of wind or jet-like outflow. Recent work by Matt and Pudritz hassuggested that if classical T Tauri stars exhibit stellar winds with mass lossrates about 0.1 times their accretion rates, the wind can carry away enoughangular momentum to keep the stars from being spun up unrealistically byaccretion. This paper presents a preliminary set of theoretical models ofaccretion-driven winds from the polar regions of T Tauri stars. These modelsare based on recently published self-consistent simulations of the Sun-scoronal heating and wind acceleration. In addition to the convection-driven MHDturbulence which dominates in the solar case, we add another source of waveenergy at the photosphere that is driven by the impact of plasma in neighboringflux tubes undergoing magnetospheric accretion. This added energy, determinedquantitatively from the far-field theory of MHD wave generation, is sufficientto produce T Tauri-like mass loss rates of at least 0.01 times the accretionrate. While still about an order of magnitude below the level required forefficient angular momentum removal, these are the first self-consistent modelsof T Tauri winds that agree reasonably well with a range of observational massloss constraints. The youngest modeled stellar winds are supported by Alfvenwave pressure, they have low temperatures -extended chromospheres-, and theyare likely to be unstable to the formation of counterpropagating shocks andclumps far from the star.

Author: Steven R. Cranmer Harvard-Smithsonian CfA

Source: https://arxiv.org/

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