Excitation of small-scale waves in the F region of the ionosphere by powerful HF radio waves

Abstract

Abstract Ionospheric small-scale waves in the F region, initiated by heating facilities in Nizhniy Novgorod, have been studied by the method of field-aligned scattering of diagnostic HF radio signals. Experimental data have been obtained on the radio path Kiev–N. Novgorod–St. Petersburg during heating campaigns with heater radiated power ERP = 20 MW and 100 MW. Observations of scattered HF signals have been made by a Doppler spectrum device with high temporal resolution. Analysis of the experimental data shows a relation between the heater power level and the parameters of ionospheric small-scale oscillations falling within the range of Pc 3–4 magnetic pulsations. It is found that the periods of wave processes in the F region of the ionosphere, induced by the heating facility, decrease with increasing heating power. The level of heating power also has an impact on the horizontal east-west component of the electric field E, the vertical component of the Doppler velocity V d and the amplitude of the vertical displacements M of the heated region. Typical magnitudes of these parameters are the following: E = 1.25 mV⧹m, V d = 6 m⧹s, M = 600–1500 m for ERP = 20 MW and E = 2.5–4.5 mV⧹m, V d = 11–25 m⧹s, M = 1000–5000 m for ERP = 100 MW. The results obtained confirm the hypothesis of excitation of the Alfven resonator by powerful HF radio waves which leads to the generation of magnetic field oscillations in the heated region giving rise to artificial Pc 3–4 magnetic pulsations and ionospheric small-scale wave processes. In this situation an increase of the heater power would lead to a growth of the electric field of hydromagnetic waves propagating in the ionosphere as well as the amplitude of the vertical displacements of the heated region.