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Ann. Geophys., 26, 1741-1749, 2008
www.ann-geophys.net/26/1741/2008/
© European Geosciences Union 2008
The formation of sporadic E layers by a vortical perturbation excited in a horizontal wind shear flow
G. G. Didebulidze and L. N. Lomidze
Georgian National Astrophysical Observatory, Ilia Chavchavadze State University, A. Kazbegi Ave. 2a, Tbilisi 0160, Georgia
Abstract. The formation of the mid-latitude sporadic E layers (Es layers) by an
atmospheric vortical perturbation excited in a horizontal shear flow
(horizontal wind with a horizontal linear shear) is investigated. A
three-dimensional atmospheric vortical perturbation (atmospheric shear
waves), whose velocity vector is in the horizontal plane and has a vertical
wavenumber kz≠0, can provide a vertical shear of the horizontal wind.
The shear waves influence the vertical transport of heavy metallic ions and
their convergence into thin and dense horizontal layers. The proposed
mechanism takes into account the dynamical influence of the shear wave
velocity in the horizontal wind on the vertical drift velocity of the ions.
It also can explain the multi-layer structure of Es layers. The pattern
of the multi-layer structure depends on the value of the shear-wave vertical
wavelength, the ion-neutral collision frequency and the direction of the
background horizontal wind. The modelling of formation of sporadic E layers
with a single and a double peak is presented. Also, the importance of shear
wave coupling with short-period atmospheric gravity waves (AGWs) on the
variations of sporadic E layer ion density is examined and discussed.
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