The band of solar wind variability at low heliographic latitudes near solar activity minimum: Plasma results from the Ulysses rapid latitude scan

J. T. Gosling, S. J. Bame, W. C. Feldman, D. J. McComas, J. L. Phillips, B. Goldstein, M. Neugebauer, J. Burkepile, A. J. Hundhausen, L. Acton

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Abstract

Near solar activity minimum large variations in the quiescent solar wind flow are confined to a narrow latitude band centered near the heliographic equator. During Ulysses' recent rapid latitude scan this band was ∼43° wide. Flow parameters poleward of the band in the opposite solar hemispheres were nearly the same. Main entry into the band of variable solar wind was via a shock disturbance most likely associated with over‐expansion of a coronal mass ejection event. Wind variability within the band was associated primarily with longitudinal structure in the solar corona and solar rotation; high‐speed streams observed there were associated with locations where the polar coronal holes extended equatorward toward the Ulysses orbit. Observations indicate that the polar coronal holes at this time occupied only ∼13% of the low corona, yet a nearly uniform high‐speed wind (average speed ∼750 km s−1) filled ∼63% of the heliosphere. This indicates the holes expanded by a factor of ∼4.8 from the low corona to interplanetary space. Much of this lateral expansion occurred beyond 1.74 solar radii from Sun center.

Original languageEnglish (US)
Pages (from-to)3329-3332
Number of pages4
JournalGeophysical Research Letters
Volume22
Issue number23
DOIs
StatePublished - Dec 1 1995
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Earth and Planetary Sciences(all)

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