The Sun and Heliosphere at Solar Maximum

Recent Ulysses observations from the Sun’s equator to the poles reveal fundamental properties of the three-dimensional heliosphere at the maximum in solar activity. The heliospheric magnetic field originates from a magnetic dipole oriented nearly perpen-dicular to, instead of nearly parallel to, the Sun’s rotation axis. Magnetic fields, solar wind, and energetic charged particles from low-latitude sources reach all latitudes, including the polar caps. The very fast high-latitude wind and polar coronal holes disappear and reappear together. Solar wind speed continues to be inversely correlated with coronal temperature. The cosmic ray flux is reduced symmetrically at all latitudes. T he space between the Sun and nearbystars is filled with ionized and neutralgas, dust, magnetic fields, and charged particles. The Sun excludes this pristine in-terstellar medium from a large volume called the heliosphere that completely encloses the planetary system. The Sun’s influence ex-tends to such great distances because the solar wind fills the heliosphere and exerts a