Symmetry in discontinuity properties at the north and south heliographic poles: Ulysses.

Abstract

A study of directional discontinuities (DDs) that occurred during 4 days of the Ulysses north polar pass was conducted (461 directional discontinuities total) using magnetic field and plasma data. We find that the total number of directional discontinuities selected by the Tsurutani and Smith (1979) method are the same in the north and south polar regions (within statistical errors) if the radial gradient is taken into account. We also find that tangential discontinuities (TDs) occur at edges of mirror mode structures. Approximately half of these structures are locally unstable. TDs are also associated with interplanetary current sheets, some of which are in regions of positive solar wind velocity 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.