Internal rotation and toroidal part of the magnetic field of AB Doradus

Abstract

We solve analytically Chandrasekhar's (1956) MHD equations for the steady parts of internal rotation and toroidal component of the magnetic field of the AB Doradus. By taking observed (Donati and Cameron 1997) surface rotation as the boundary condition and assuming that the base of the convection zone rotates rigidly, we estimate the size of the convective envelope to be 40% of the radius and the rotation velocity at the base to be not less than 1.42 x 10-4 rad/sec. We deduce that the toroidal magnetic field is distributed throughout the convective envelope. By taking the average density of 1.78gm cm-3 and radius 5.95 x 1010 cms (Allen 1972), we obtain a Mega gauss field near base of the convective envelope. We present rotational and toroidal magnetic field profiles in the interior, and conjecture on the time dependent part of the magnetic field.