Ulysses at 50° south: constant immersion in the high‐speed solar wind

J. L. Phillips, A. Balogh, S. J. Bame, B. E. Goldstein, J. T. Gosling, J. T. Hoeksema, D. J. McComas, M. Neugebauer, N. R. Sheeley, Y. ‐M Wang

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Abstract

We present speed observations from the Ulysses solar wind plasma experiment through 50° south latitude. The pronounced speed modulation arising from solar rotation and the tilt of the heliomagnetic current sheet has nearly disappeared. Ulysses is now observing wind speeds in the 700 to 800 km s−1 range, with a magnetic polarity indicating an origin in the large south polar coronal hole. The strong compressions, rarefactions, and shock waves previously seen have weakened or disappeared. Occasional coronal mass ejections characterized by low plasma density caused by radial expansion have been observed. The coronal configuration was simple and stable in 1993, indicating that the observed solar wind changes were caused by increasing spacecraft latitude. Trends in prevailing speed with increasing latitude support previous findings. A decrease in peak speed southward of 40° latitude may indicate that the fastest solar wind comes from the equatorial extensions of the polar coronal holes.

Original languageEnglish (US)
Pages (from-to)1105-1108
Number of pages4
JournalGeophysical Research Letters
Volume21
Issue number12
DOIs
StatePublished - Jun 15 1994
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Earth and Planetary Sciences(all)

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    Phillips, J. L., Balogh, A., Bame, S. J., Goldstein, B. E., Gosling, J. T., Hoeksema, J. T., McComas, D. J., Neugebauer, M., Sheeley, N. R., & Wang, Y. M. (1994). Ulysses at 50° south: constant immersion in the high‐speed solar wind. Geophysical Research Letters, 21(12), 1105-1108. https://doi.org/10.1029/94GL01065