Possible ionospheric preconditioning by shear flow leading to equatorial spread F

Other literature type English OPEN
Hysell, D. L. ; Kudeki, E. ; Chau, J. L. (2005)
  • Journal: (issn: 1432-0576, eissn: 1432-0576)
  • Related identifiers: doi: 10.5194/angeo-23-2647-2005
  • Subject:
    arxiv: Physics::Geophysics | Physics::Space Physics

Vertical shear in the zonal plasma drift speed is apparent in incoherent and coherent scatter radar observations of the bottomside <i>F</i> region ionosphere made at Jicamarca from about 1600–2200 LT. The relative importance of the factors controlling the shear, which include competition between the <i>E</i> and <i>F</i> region dynamos as well as vertical currents driven in the <i>E</i> and <i>F</i> 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 telltale 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 <i>F</i>. 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.<br><br> <b>Keywords.</b> Ionosphere (Equatorial ionosphere; ionospheric irregularities) – Space plasma physics (Waves and instabilities)
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