External production and control of electrojet irregularities.

Analytical investigation of parametric coupling of a large-amplitude 'pump' wave to a natural plasma mode of the ionospheric E layer. It is shown that the E layer plasma mode can be either stabilized or destabilized by the parametric process. Two necessary conditions for parametric interaction are (1) near frequency matching (i.e., the pump wave frequency should be near the local upper hybrid frequency) and (2) a finite electric field component of the pump wave perpendicular to the background static magnetic field. An investigation of the propagation characteristics of the pump wave in the magnetic equatorial region indicates that an obliquely propagating O mode in the magnetic meridian plane meets the two necessary conditions in an optimal manner. From typical values of ionospheric parameters it is estimated that the required incident energy flux of the pump wave for parametric stabilization or destabilization of the E layer plasma mode (near its natural marginal stability) is much less than 1 mW/sq m. Thus parametric coupling experiments for the ionospheric E layer are technically feasible.