Magnetic braking and angular momentum transport

The redistribution of angular momentum in a non-uniformly rotating plasma, permeated by a larger scale frozen-in magnetic field and symmetric about the rotation axis, was investigated analytical. Due to the twisting of the poloidal magnetic field lines arising from the non-uniform rotation, magnetic torques are exerted on the plasma which try to suppress the rotational shear. There is a consequent transport of angular momentum, via torsional Alfven waves propagating along the magnetic field lines, from the more rapidly to the more slowly rotating parts of the plasma. A spherical, uniformly dense central core of plasma, or blob, of fixed radius is imagined to be rotating differentially with respect to the surrounding medium, and initially the blob and its environs are given uniform angular velocities (LAMBDA) and (LAMBDA)0 respectively. Two models of the frozen-in poloidal magnetic field linking the blob to its surroundings are considered. The equations describing the interaction between the magnetic and rotation fields were solved by Laplace transformation techniques.