Alfvén waves with periods from <1 to >10 hours are shown to be continuously present in the sun's south and north polar regions. Below ≈ 30° latitude, as revealed by the rapid traversal of the equatorial region by Ulysses, the wave power averaged over a solar rotation decreases abruptly. The correlations between magnetic field and solar wind velocity fluctuations, upon which the wave identification is based, indicate outward propagation in both hemispheres. The Ulysses observations are consistent with many of the properties of Alfvén waves seen in the ecliptic in association with high speed streams. Some implications of the waves in the polar regions are explored. Because of the long wavelengths, which reach ≈ 0.3AU, the waves resonate with 10–10³MeV/nucleon galactic cosmic rays and oppose their entry into the polar caps. The wave amplitudes imply a contribution to the acceleration of the high latitude wind due to momentum transfer of only a few percent.
All Science Journal Classification (ASJC) codes
- Earth and Planetary Sciences(all)