SSP seminar

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

Steven R. Cranmer (CfA)

Monday 28th January 2008, 12:00
Pratt conference room, 60 Garden Street

Pre-main-sequence stars are observed to be surrounded by both accretion flows and some kind of wind or jet-like outflow. There are several possible explanations of how and where the outflows arise, including disk winds, X-winds, impulsive (CME-like) ejections, and "true" stellar winds. Whatever their origin, the outflows produce observational diagnostics that indicate mass loss rates exceeding the Sun's present mass loss rate by factors of a thousand to a million. Recent work by Matt and Pudritz has suggested that if there is a stellar wind with a mass loss rate about 10% of the accretion rate, the wind can carry away enough angular momentum to keep T Tauri stars from being spun up unrealistically by the accretion. In this talk, I will present 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), I add a 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 is enough to produce large mass loss rates, but it is still uncertain whether it is enough to solve the T Tauri angular momentum problem.


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