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

TL;DR

This paper develops theoretical models of polar winds in T Tauri stars driven by turbulence and magnetospheric accretion, producing mass loss rates consistent with observations and providing insights into stellar wind properties.

Contribution

It introduces self-consistent models of T Tauri winds incorporating accretion-driven wave energy, extending solar wind theories to young stellar objects.

Findings

Mass loss rates of at least 0.01 times the accretion rate achieved.

Winds supported by Alfven wave pressure with extended chromospheres.

Predicted winds are likely unstable to shocks and clumping.

Abstract

Pre-main-sequence stars are observed to be surrounded by both accretion flows and some kind of wind or jet-like outflow. Recent work by Matt and Pudritz has suggested that if classical T Tauri stars exhibit stellar winds with mass loss rates about 0.1 times their accretion rates, the wind can carry away enough angular momentum to keep the stars from being spun up unrealistically by accretion. This paper presents a preliminary set of theoretical models of accretion-driven winds from the polar regions of T Tauri stars. These models are based on recently published self-consistent simulations of the Sun's coronal heating and wind acceleration. In addition to the convection-driven MHD turbulence (which dominates in the solar case), we add another source of wave energy at the photosphere that is driven by the impact of plasma in neighboring flux tubes undergoing magnetospheric accretion. This added energy, determined quantitatively from the far-field theory of MHD wave generation, is sufficient to produce T Tauri-like mass loss rates of at least 0.01 times the accretion rate. While still about an order of magnitude below the level required for efficient angular momentum removal, these are the first self-consistent models of T Tauri winds that agree reasonably well with a range of observational mass loss constraints. The youngest modeled stellar winds are supported by Alfven wave pressure, they have low temperatures ("extended chromospheres"), and they are likely to be unstable to the formation of counterpropagating shocks and clumps far from the star.