Volumes and Issues  Contents of Issue 7

Ann. Geophys., 23, 2647-2655, 2005
www.ann-geophys.net/23/2647/2005/
© European Geosciences Union 2005

Possible ionospheric preconditioning by shear flow leading to equatorial spread F

D. L. Hysell¹, E. Kudeki², and J. L. Chau^3
1Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, NY 14853, USA
²Department of Electrical and Computer Engineering, University of Illinois, Urbana, Il 61801, USA
³Radio Observatorio de Jicamarca, Instituto Geofísico del Perú, Lima, Perú

Abstract. Vertical shear in the 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 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 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.

Keywords. Ionosphere (Equatorial ionosphere; ionospheric irregularities) – Space plasma physics (Waves and instabilities)

Full Article (PDF, 1779 KB)

Citation: Hysell, D. L., Kudeki, E., and Chau, J. L.: Possible ionospheric preconditioning by shear flow leading to equatorial spread F, Ann. Geophys., 23, 2647-2655, 2005.   Bibtex   EndNote   Reference Manager