Pre‐main sequence stellar activity

Models of stellar activity based on the α–ω dynamo have recently been proposed by B ELVEDERE et al. (1980c, 1981b) for main sequence and giant late type stars. In the present work we extend the theoretical analysis to the pre‐main sequence fully convective phase of stellar evolution. As a measure of magnetic activity we assume the intensity of the toroidal magnetic field B t . The results show that B t decreases with the increasing effective temperature along the evolutionary track of a star of given mass. It is stressed the crucial dependence of the intensity of the magnetic field on the rotation rate. Comparison with the observations of pre‐main sequence stellar activity in the very young galactic cluster NGC 2264 is briefly discussed.