The Signatures of Structured Winds in T Tauri Stars

The identification of He I lines λ 4471.5 A, λ 5875.6 A, λ 6678.1 Aand He II lines λ 4685.7 Ain emission in the optical spectra of T Tauri stars (e.g. Penston & Keavey 1977, Lago & Penston 1982) was the first clear indication for a temperature structure in the outer layers of these stars. Yet no immediate explanation was proposed for the presence of those high temperature regions in the atmosphere of late type stars.