Observations of ionospheric modification by the Tromsø heating facility with the mobile diagnostic equipment of IZMIRAN

Results are presented of ionospheric modification experiments carried out at Tromsø, Norway, in October and November 1988. These experiments were jointly conducted by IZMIRAN and MPAe. In these experiments, small scale electron density perturbations (having a vertical size ~ 1 km and a density variation ~0.1%) were found to be excited near the reflection and upper hybrid resonance (UHR) points of an O-mode pump wave. When the pump frequency was close to the triple electron gyrofrequency, there were no noticeable perturbations near the UHR point. This peculiarity correlated well with a decrease of the intensity of stimulated electromagnetic emission (SEE). When SEE is comparatively weak, the SEE intensity can vary quasi-periodically, with a quasi-period of approximately 1 s. When this happens, anticorrelations between different parts of the SEE spectrum become possible.