Cool Stars 14 - Submitted Abstract # 219 This version created on 05 October 2006 The Structured Chromosphere and Wind of TW Hya Andrea K. Dupree, CfA Nancy S. Brickhouse, CfA Eugene H. Avrett, CfA Steven R. Cranmer, CfA Tamas Szalai, University of Szeged The nearby accreting T Tauri star, TW Hya is viewed almost pole-on so it provides an opportunity to examine its accretion and wind characteristics. A continuous set of echelle spectra of TW Hya, taken with MIKE on Magellan2 in April 2006 reveals systematic variations in the flux, velocity, and the profile of the H-alpha emission line. These variations appear to be consistent with the photometric period of 2.8 days. Absorption features reoccur at high velocity (100 and 200 km/s) in the wind. Additional spectra from 2004 show a similar repetitive pattern. This behavior suggests that: (a) accretion is not uniformly distributed over the stellar hemisphere in view; (b) stable structures are present in the chromosphere, most likely due to the stellar magnetic field configuration. Semi-empirical models of the atmosphere have been constructed to compute line profiles using the PANDORA code and define the wind structure. These calculations suggest the mass loss rate is variable and comparable to the mass accretion rates in the literature, requiring a very efficient mechanism if the wind is powered only by accretion. ----------------------------------