Ionosphere thermal response to a HF radio wave interaction, during artificial 5577Å airglow enhancements at a sporadic E layer

This article studies an experiment of artificial modification of the ionosphere by HF radio waves transmitted by a ground-based antenna in Arecibo, i.e, at a mid-latitude ionosphere. The peculiarity and uniqueness of this experiment (just one more time a similar event has been recorded) is that during its realization a sporadic E layer (or, Es layer) appeared unexpectedly and caused total blocking of the F-region of the ionosphere and artificial 5577Å (green) airglow enhancements originated in the Es layer. We present estimations of the energy rates due to ohmic heating and the decay of parametric instabilities, as a result of the interaction of the Es layer with the transmitted high-power HF O-mode radio waves, both during the initial stage of the Es layer growth and later when the electron density in the Es layer decreased. Analytical expressions of the electric field of the HF wave, ionospheric electric conductivity and heating rates are inserted into the calculations, using initially the Airy function and in the second stage the Weber function to describe the heater’s electric field in its reflection region. The subsequent spatial and temporal changes in electron temperatures are estimated. The results show that the electron temperatures demonstrate significant increase above their unperturbed values, but not sufficient enough to justify thermal excitation of the green airglow.