Heliospheric magnetic field polarity inversions at high heliographic latitudes

The heliospheric magnetic field over the poles of the sun has been examined to identify intervals when the polarity of the magnetic field deviates significantly from the calculated Parker spiral, using Ulysses observations in 1994 and 1995, near solar minimum. Intervals with deviation > 90 degrees have been identified, corresponding to magnetic field vectors pointing in the hemisphere opposite to that of the dominant polarity in the high speed solar wind originating in the polar coronal holes. The number of inversion periods decreases as the averaging period is increased from 1 to 12 hours. Their distribution was found to vary in time over the northern solar pole, where the average direction also deviated from the Parker direction. The propagation direction of waves during polarity inversions show that these are caused by large-scale folds in the magnetic field, rather than by opposite polarity magnetic flux tubes originating near the sun.