Effective radius of ionospheric E-layer heating by powerful HF radiation

This paper presents a theoretical analysis of radial distributions for electron temperature T e and density n e examined in the ionospheric region located at E-layer altitudes and heated by powerful HF radiation. It has been found that the effective radius of this heating r eff is shorter than the characteristic radius of the radiation spot a (i.e. shorter than the radius of the ionospheric region exposed to the radiation at a given altitude), when the amplitude of the electric field E m at the center of the radiation spot is below the characteristic plasma field E p, and r eff>a for E m> E p. At the boundary of the heating region (r=r eff), the radial scale of T e variation is shorter than that of the electric field squared, i.e. comparatively strong gradients of n e and T e are formed at both E mp and E m>E p.