T Tauri winds

Abstract

The problem of mass loss from T Tauri stars is addressed. It is shown that, as deduced from the H-alpha line intensity alone, the mass loss rates from the 'average' T Tauri star have an ambiguity of at least three orders of magnitude. In the case of mass loss rates less than approximately 10 to the -9th solar mass per year, thermal coronal expansion or line radiation pressure is considered a possible wind mechanism. For rates between 10 to the -9th and a few x 10 to the -8th solar mass per year, the deposition of the momentum of Alfven waves generated in a convection zone is thought to be a plausible mechanism. A model is presented in which a rotating star has a wind driven by this mechanism, and simplified examples are displayed. No acceptable mechanism is found in the 'average' T Tauri star for maintaining a wind with strength greater than a few x 10 to the -8th solar mass per year.