AN INVESTIGATION OF THE STRUCTURE OF ROTATIONAL DISCONTINUITIES

The structure of rotational discontinuities (RDs) has been studied through hybrid simulations for a range of propagation angle circled-x-bn between the discontinuity normal and the upstream magnetic field and plasma beta. For sufficiently narrow initial states, the simulations produce quasi-steady "reverse rotation" magnetic field structures for 30-degrees less-than-or-equal-to THETA-bn less-than-or-equal-to 60-degrees and 0 < beta less-than-or-equal-to 1 on a time scale of roughly 200 OMEGA-i-1. This structure is characterized by a right handed field rotation upstream joined smoothly to a left handed field rotation downstream; its width decreases from 60-70 c/omega-pi at circled-x-bn = 30-degrees to less than 25 c/omega-pi at THETA-bn = 60-degrees. The magnetic field hodograms of our RD results have a distinctive S-shape which is most pronounced in simulations with small THETA-bn and initially right handed rotations. The reverse rotation structure is the net result of the expansion of the initial current layer via the fast and intermediate wave modes.