A direction‐dependent instability of sporadic‐E layers in the nighttime midlatitude ionosphere

摘要: [1] The configuration of a midlatitude sporadic-E (Es) layer at zonal wind-shear node has been assumed to be stable equilibrium, as long the wind shear is hydrodynamically stable. In this paper, we show that equilibrium in fact unstable, night, electrodynamical forces arise when plane wave perturbations altitude or density are imposed on Es layer. We growth rate instability depends azimuthal alignment phase fronts plane-wave distortion, feature reminiscient Perkins [Perkins, 1973]. The dependence azimuth consistent with observations structure layers same preferred alignment.