Possible ionospheric preconditioning by shear flow leading to equatorial spread F

Dave L. Hysell, E. Kudeki, J. L. Chau

Research output: Contribution to journalArticlepeer-review


Vertical shear in th zonal plasma drift speed is apparent in incoherent and coherent scatter radar observations of the bottomside F region ionosphere made at Jicamarca from about 1600-2200 LT. The relative importance of the factors controlling the shear, which include competition between the E and F region dynamos as well as vertical currents driven in the E and F regions at the dip equator, is presently unknown. Bottom-type scattering layers arise in strata where the neutral and plasma drifts differ widely, and periodic structuring of irregularities within the layers is tell-tale of intermediate-scale waves in the bottomside. These precursor waves appear to be able to seed ionospheric interchange instabilities and initiate full-blown equatorial spread F. The seed or precursor waves may be generated by a collisional shear instability. However, assessing the viability of shear instability requires measurements of the same parameters needed to understand shear flow quantitatively - thermospheric neutral wind and off-equatorial conductivity profiles.

Original languageEnglish (US)
Pages (from-to)2647-2655
Number of pages9
JournalAnnales Geophysicae
Issue number7
StatePublished - 2005


  • Ionosphere (Equatorial ionosphere; ionospheric irregularities)
  • Space plasma physics (Waves and instabilities)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Geology
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science


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