We study the modification effects of the high-latitude ionospheric F region induced by a highpower O-mode HF radio wave injected towards the magnetic zenith, at frequencies near the fifth and sixth electron gyroharmonics using the EISCAT/Heating facility. Multi-instrument diagnostics with the EISCAT incoherent scatter radar (930 MHz) at Tromsø, Norway, the CUTLASS coherent radar at Hankasalmi, Finland, and stimulated electromagnetic emission (SEE) receiver at Tromsø, has been used for analysis of the observed phenomena. The behavior of the ionospheric plasma parameters (electron’s density and temperature), small-scale artificial field-aligned irregularities, plasma and ion-line spectra, and ionospheric SEE are analyzed in detail. Modification effects near the fifth and sixth electron gyroharmonics have been compared. The coexistence of the thermal (resonance) parametric instability, parametric decay (striction) instability, and/or oscillating two-stream instability was found at these frequencies. The excitation of instabilities occurred at altitudes close to the reflection altitude of the HF pump wave and at the altitudes of the upper-hybrid resonance.
S. M. Grach, Interaction Between the High-Power Radio Waves and the Ionosphere, Part 1, Excitation of the Plasma Turbulence in the Upper Ionosphere, a manual [in Russian], Nizhny Novgorod State Univ., Nizhny Novgorod (2012).Google Scholar