Magnetic activity in young stellar objects caused by tearing instabilities

Magnetic activity phenomena are characteristic for T-Tauri stars as well as protostellar class I objects. A model for the flare-like emissivity based on a macroscopic plasma instability, the resistive tearing mode, is proposed. The dispersion relation for the unstable modes for the appropriate partially ionized dusty plasma regime is presented and solved numerically. The results indicate that tearing instabilities operating in current sheets formed within magnetic flux tubes that basically constitute magnetospheres around young stellar objects are a possible explanation for the temporal variability and spatial extensions of bursty radiation emitting regions around T-Tauri stars.