Ulysses paper

Adv. Space Res., in press, 2000

Abstract:
Ulysses recently completed a second slow latitude scan of the northern helosphere, a descent from 80.2 degrees North in July 1995 to the solar equator in December 1997. These recent magnetic field observation complement those from the south hemisphere and reveal new features as well as the effect of the changing solar cycle. Five topics are emphasized in this report. (1) The solar wind latitude structure is affected by the low inclination of the heliosphere current sheet (HCS) which prevents fast high latitude wind from reaching down into the ecliptic and leads to three distinct zones, the middle or transition zone consisting of large periodic Corotating Interaction Regions (CIRs). The HCS is first observed in the middle zone at unexpectedly high latitudes. (2) In the Corotating Rarefaction Regions (CRRs) separating the CIRs, a large discrepancy is found between the observed and Parker spiral angles with the field being underwound by around 30 degrees. (3) Fluctuations in the field are again predominantly Alfven waves in the fast winds so that the variances undergo periodic variation in level in the transition zone. (4) The magnetic flux parameter, r2Br, differs in the three zones being constant at high latitudes, enhanced in mid- and depleted at low- latitudes. The observations are consistent with displacement of magnetic flux from low to mid-latitudes. (5) An asymmetry between the radial components in the south and north hemispheres is evident in the observations being made in the ecliptic by WIND. The observations agree with a southward displacement of the HCS as inferred from the Ulysses cosmic ray measurements. A time variation during the fast latitude scan from the south to the north pole obscured this asymmetry in the Ulysses magnetic field measurements.

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