Ulysses observations of Alfvén waves in the southern and northern solar hemispheres

E. J. Smith, A. Balogh, M. Neugebauer, D. McComas

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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.

Original languageEnglish (US)
Pages (from-to)3381-3384
Number of pages4
JournalGeophysical Research Letters
Issue number23
StatePublished - Dec 1 1995
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Geophysics
  • General Earth and Planetary Sciences


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