Warm disk coronae in classical T Tauri stars

It is proposed that a warm disk corona is a characteristic feature of the accretion process in a classical T Tauri star, based on analyses of the [O I] lambda lambda 6300, 5577 emission and the central absorptions in the Balmer lines of hydrogen. Calculations are presented to determine the physical conditions needed to produce the hydrogen and O I excitation. They indicate that a substantial fraction of the energy released in the accretion of matter through the disk may be dissipated at the disk surface in order to heat the corona.