Latitudinal structure of the heliospheric current sheet and corotating streams measured by WIND and ULYSSES

Abstract

All heliospheric current sheet (HCS) crossings and corotating solar wind streams detected by both WIND and Ulysses have been identified. These measurements were made when Ulysses was in its fast latitudinal scan (at a heliocentric radial distance of ∼1.4 AU) and WIND was in the ecliptic plane near the Earth. Instantaneous solar wind velocities are used to map the locations of the HCS crossings and plasma sources back to the solar surface. The HCS crossing locations have been compared with those predicted by the Stanford source surface magnetic field model. In general, both locations correspond closely, but there is an error range up to 25° in heliographic longitude. These discrepancies in the HSC locations may be due to an overly southward displacement (∼6°) in the model. We have also found that six pairs of corotating streams from 11 pairs of candidate streams have the same sources and were detected by both spacecraft at widely separated latitudes. Under an assumption of the absence of temporal variations, a velocity change of ΔV ≈ 750 e−0.38Δθ (km/s/degree) has been determined as a function of the angular distance, Δθ, from the HCS.