Observation of nonlinear interactions in large-scale density enhancements of the high-latitude ionosphere

Simultaneous measurements of electron density and ELF electric field by the AUREOL-3 satellite have allowed Cerisier et al. [1985] to point out the ex istence of large-scale density irregularities in the high-latitude topside F region and to establish the role of the gradient drift instability in the plasma structuring. High-resolution spectra of the density and field fluct uations show the presence of low-frequency peaks linked by relationships su ch that f(m)+ f(n) = f(m+n). Bispectral analyses point out nonlinear intera ctions between waves at 7.8 and 15.6 Hz and density irregularities at 5.85 Hz. The consistency of the results with regard to instability models is dis cussed. The existence of an interaction process involving Schumann resonanc es is suggested.