Production of electric field perturbations by gravity wave winds in the E region suitable for initiating equatorial spread F

Abstract

This study proposes a new mechanism through which electric field perturbations, which map up to the F region base, can be generated by gravity wave winds. These fields are produced efficiently when gravity waves interact with thin E layers or sporadic layers in the low latitude E region. The proposed mechanism operates in two steps. In step 1, eastward zonal winds in the F region produce radially downward electric fields. These fields map down to the E region producing downward transport of plasma. This reduces the thickness of the E layer and help in formation of sporadic layers. In step 2, gravity wave winds interact with the above created layers and produce electric field perturbations. This interaction is through (i) dynamo action and (ii) zonal currents driven by the F region dynamo field flowing in the E region whose conductivities are perturbed. These perturbations are caused when gravity wave winds produce electron density irregularities. This work demonstrates that with a thin plasma layer in the E region, the electric field perturbations are mainly produced through Hall conductivity. In previously proposed studies, the electric field perturbations were mainly attributed to Pedersen conductivity. The electric field perturbations produced through the proposed mechanism are much larger than those through earlier mechanisms and have characteristics that are suitable for the growth of seed irregularities in the F region base. The characteristics of these seed irregularities are such that they can grow into the equatorial Spread F irregularities through the Rayleigh Taylor instability mechanism.