SYMMETRY IN DISCONTINUITY PROPERTIES AT THE NORTH AND SOUTH HELIOGRAPHIC POLES - ULYSSES

A study of directional discontinuities (DDs) that occurred during 4 da ys of the Ulysses north polar pass wets conducted (461 directional dis continuities total) using magnetic field and plasma data. We find that the total number of directional discontinuities selected by the Tsuru tani and Smith (1979) method are the same in the north and south polar regions (within statistical errors) if the radial gradient is taken i nto account. We also find that tangential discontinuities (TDs) occur at edges of mirror mode structures. Approximately half of these struct ures are locally unstable. TDs are also associated with interplanetary current sheets, some of which are in regions of positive solar wind v elocity gradients. To first order, we find no difference in the number of directional discontinuities, number of TDs, or the types of TDs in the north polar region from the south polar region.