The influence of the Sun's magnetic field on energetic particles at high heliospheric latitudes

Abstract

The first passage of the Ulysses spacecraft to high latitudes was during the declining phase of solar cycle 22. The recent second passage to high latitudes was close to the maximum of solar cycle 23. The axis of the dipolar component of the Sun's magnetic field was close to 90° from the spin axis, and the coronal neutral line extended up to high latitudes. A variable but generally slow solar wind was observed all the way up to the highest latitudes reached by Ulysses, as was the sector structure of the magnetic field. The high‐latitude heliosphere was populated with intensities of energetic particles with energies around 1 MeV several orders of magnitude above background. We show how the changes in the Sun's magnetic field, the coronal holes, and the configuration of the heliosphere could be responsible for the differences between particle observations in the two orbits.