Ulysses paper

Geophys. Res. Lett., 26, 631-634, 1999

Abstract:
The structure of the heliospheric magnetic field over the polar regions of the sun has been examined to identify periods in which the polarity of the magnetic field deviates significantly from the calculated Parker spiral direction. A number of periods have been identified in which the deviation is >90 degreees, corresponding to magnetic field vectors pointing in the hemisphere opposite to that of the dominant polarity in the polar coronal holes. The number of such inversion periods decreases significantly as the averaging period of the field is increased from 1 to 12 hours. Their distribution was found to vary in time over the northern solar pole, where the azimuthal angle of the magnetic field also deviated systematically from the Parker direction. Two examples of polarity inversion 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.

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