Meeting abstract

IAGA, 8th Scientific Assembly, Uppsala, Sweden, 4-8 August, 1997

Abstract:
Over the past few years the magnetometer experiment onboard the Ulysses spacecraft has provided a comprehensive survey of the configuration and properties the heliospheric magnetic field over the polar coronal hole regions of the Sun at a time of solar minimum activity. By studying distributions of the magnetic field direction accumulated over time periods equivalent to many solar rotation periods we have analysed the extent to which the underlying field direction differs from that predicted by the simple Parker spiral model. In the southern hemisphere we found that at latitudes greater than 60°S the most probable field azimuth angle corresponded to magnetic field lines of the order of 24° more tightly wound than predicted by the spiral model, while the meridional (or north-south) angle remained in good agreement with the model. In the northern hemisphere we found that the most probable azimuth angle agreed with the prediction throughout, but the most probable meridional angle showed systematic deviations from the expected 0°. For example, taking a distribution over latitudes above 60°N, an apparent 8° deflection equatorwards was noted, with some evidence of there being a double peak in the distribution. We investigate possible explanations for the shape of these distributions, including the possibility of heliolongitude effects that might have been averaged over in our long time period distributions.