Two-dimensional nonlinear processes associated with ‘type 1’ irregularities in the equatorial electrojet

Abstract

It is suggested that the stabilization mechanism of type 1 irregularities in the equatorial electrojet has two aspects: (1) the turbulence tends to inhibit the formation of large currents and to maintain the plasma in a state relatively ‘close’ to linear marginal stability, and (2) in this state, energy is transferred by two-dimensional nonlinear wave-coupling processes from the linearly growing modes to linearly damped ones propagating in other directions. Energy transfer processes can thus provide detailed stabilization over the entire spectrum. It is argued that (1) the theory provides a plausible interpretation of the as yet puzzling experimental result that the irregularities appear more or less simultaneously over a substantial range of radar elevation angles and (2) the fact that their phase velocities are close to the sound speed and often completely independent of the direction of propagation is perhaps a consequence of mode coupling, but definite prediction here requires numerical calculations.