Direct observational evidence for a heliospheric magnetic field with large excursions in latitude

Fisk has pointed out that the heliospheric magnetic field in fast solar wind, that is, at the higher heliographic latitudes, may undergo large excursions in heliographic latitudes, and thus that the field will deviate from the expected Archimedes spiral pattern. These excursions result from the interplay between the nonradial expansion of the solar wind in rigidly rotating coronal holes and the differential rotation of the footpoints of the field Lines anchored in the photosphere. In this paper magnetic field data from the Ulysses spacecraft in the southern solar hemisphere are analyzed and show that the field exhibits the systematic variations with latitude and longitude expected from the field configuration predicted by Fisk. We also show that variations about the predicted field should exhibit a unique periodicity of about 20 days at high latitudes and that the predicted periodicity is in fact observed. The observation conformation of the predicted field provides support for several other applications of this theory.