Features of small-scale artificial irregularities in the high latitude ionospheric F-region from remote sensing observations

Powerful HF radio waves interacting with the ionosphere accelerate or heat electrons, pushing the ionospheric plasma out of equilibrium and leading to the creation of various non-linear phenomena. One of the most prominent phenomena discovered from HF heating experiments is the generation of small-scale artificial field-aligned irregularities (AFAI). AFAI induce bi-static scattering of HF and VHF signals, providing their propagation in the frequency range and over distances unattainable in the natural ionosphere. This makes it possible to create HF-driven radio communication channels. We present results from an EISCAT/Heating (Tromsø, Norway) experiment on 18 February 2013, concerning the features and behaviors of AFAI in the high latitude ionospheric F-region induced by high power HF radio waves with O- and X-mode polarization using the bi-static scatter method. Joint use of various remote diagnostics tools, including the multichannel HF Doppler equipment, oblique sounding and the CUTLUSS backscatter radar provides a more comprehensive and complete AFAI study, including the size of the artificially disturbed region occupied with AFAI, the frequency band of bi-static scatter signals (BSS), the fine structure of BSS, the intensity, growth and decay times of AFAI. It has been found that O- and X-mode AFAI have different characteristics and generation mechanisms.

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