Imaging radar observations and nonlocal theory of large-scale plasma waves in the equatorial electrojet

摘要: Abstract. Large-scale ( l ~ 1 km) waves in the daytime and night-time equatorial electrojet are studied using coherent scatter radar data from Jicamarca. Images of plasma irregularities within main beam formed interferometry with multiple baselines. These images analyzed according to nonlocal gradient drift instability theory also compared nonlinear computer simulations carried out recently by Ronchi et al. (1991) Hu Bhattacharjee (1999). In daytime, large-scale assume a non-steady dynamical equilibrium state characterized straining destruction shear diffusion followed spontaneous regeneration as predicted (1991). At night, when steep density gradients emerge, slowly propagating vertically extended predominate. Eikonal analysis suggests that these trapped (absolutely unstable) or nearly (convectively able tunnel between altitude regions which locally unstable. Intermediate-scale mainly transient stable) but can become absolutely unstable narrow bands determined background profile. characteristics consistent presented A new class primary is found occur along sweep westward downward high altitudes through E-region at twilight. Key words. Ionosphere (equatorial ionosphere; ionospheric irregularities; instabilities)