  We present a full-scale simulation study of a generalized Zakharov model for
the generation of the topside electrostatic turbulence due to the parametric
instability during ionospheric heating experiments near the F region peak. The
nonlinear tunneling of electromagnetic waves through the ionospheric layer is
attributed to multiple-stage parametric decay and mode-conversion processes. At
the bottomside of the F region, electrostatic turbulence excited by the
parametric instability results in the conversion of the ordinary (O mode) wave
into a large amplitude extraordinary (Z mode) wave tunneling through the F
peak. At the topside interaction region, the Z mode undergoes parametric decay
cascade process that results in the generation of the topside electrostatic
turbulence and then conversion process yielding O waves that escape the plasma.
This study may explain the observed topside ionospheric turbulence during
ground based ionospheric heating experiments.
