Ulysses in the south polar cap at solar maximum: Heliospheric magnetic field

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Abstract
Observations during the recent ascent of Ulysses to the south polar region are reported. Large variations in field magnitude are associated principally with solar wind interaction regions. The observed spiral angle agrees reasonably well with the Parker model. The magnetic flux, the product of the radial field component and the square of the radial distance (r² BR), is independent of latitude implying non‐radial expansion of the solar wind. Two magnetic sectors are present up to a latitude of ≈ −78° above which a single negative (inward) polarity is observed consistent with the polar field not yet having reversed. Crossings between sectors, extrapolated back to the sun, appear consistent with a single warped current sheet tilted slightly to the rotation axis. Field lines in the polar region passing near the current sheet originate at low latitudes. They provide access of high energy solar particles to the polar region.