Meeting abstract

AGU Fall Meeting, San Francisco, 15-19 December 1996

Abstract:
Ulysses has now completed its first passages through both the south and north polar regions of the heliosphere. Previous work on the underlying magnetic field direction using data from the magnetometer experiment on Ulysses showed that the most probable azimuth angle in the high latitude (greater than 60°S) southern polar heliosphere was of the order of 24° more tightly wound than expected from the simple spiral model. Recently, our first analysis of the field direction at the same high latitudes in the north polar heliosphere revealed that similar overwinding was not present and that the most probable azimuth angle agreed with the model prediction. Here we report on a more detailed analysis of the underlying field direction over the complete northern hemisphere pass. While we find that the most probable azimuth angle follows the predicted spiral direction throughout, there is some evidence of systematic deviations in the meridional (north-south) angle which were not seen in the southern hemisphere. We summarise the differences between the northern and southern hemispheres and investigate possible explanations.