Interplanetary discontinuities in corotating streams and their interaction regions.

Abstract

In this study, we investigate the discontinuity properties in the low latitude corotating stream regions which are encountered during Ulysses traveling from the south to north heliographic poles in 1995. Through the occurrence rates of directional discontinuities and tangential discontinuities, we find that there are three different regions around a high speed stream. The leading edge regions of the stream have the occurrence rate about 50DDs/day and 10TDs/day. These TDs are mostly associated with HCS crossings. Plasma β and anisotropy R are relatively low. In the stream velocity peak region, the magnetic field magnitude is low and stable. The occurrence rate of DDs is twice as high as in other two regions, but there are very few or no TDs. The stream trailing regions have similar occurrence rates of DDs and TDs to the leading edge regions. However, the structures of the TDs are significant different. These TDs are mostly found at the edges of mirror-mode structures and with large β and anisotropy ratios R.