Modification of the earth’s ionosphere by high-power HF radio emission: Artificial periodic inhomogeneities and the sporadic E layer

Abstract

We present the results of new studies of the sporadic E layer in the case of heating of the ionosphere by high-power HF radio emission. The measurements were performed at the "Sura" heating facility. Ionosphere was modified by high-power radio emission from the "Sura" facility and was sounded by the probing radio waves of the same frequency and mode. The heating of the ionosphere resulted in the formation of artificial periodic inhomogeneities, and an increase in the intensity of all signals scattered by the D, E, and F regions and the sporadic E layer by 5-20 dB was observed. The increase was observed during heating of the ionosphere by each magnetoionic component, but was smaller for heating by an ordinary-mode wave. This effect was resonant and disappeared as a result of the frequency detuning down to 85 kHz. During the ionospheric modification, the signal-intensity increased due to modulation of the natural profile of the electron number density by the artificial periodic structure.

Results of studying the sporadic E layer by the method of resonant scattering of radio waves by artificial periodic inhomogeneities of the ionospheric plasma

“…The next experiment was performed in July 2006 in the daytime, usually from 9:00 to 18:00 LT [30]. As a rule, stable sporadic layers were observed in that period.…”

“…However, a relatively long time of action on the layer [5][6][7] is, as a rule, required. Progress in this direction will be possible if novel diagnostic techniques are employed [21,26,29,30].…”

“…A thick diffusional E s layer and a thin E s "sublayer" (the E s layer located below the E-region maximum is often called the "sublayer") were often observed at altitudes 100−120 and 85−90 km, respectively. Illustrations and a detailed discussion of this interesting effect are presented in [30].…”

Artificial periodic irregularities in the high‐latitude ionosphere excited by the HAARP facility

“…[, , ]. The most recent experiments on the API formation were carried out using similar pumping and probing waves [ Bakhmet ' eva et al ., , , ; Bakhmetieva and Belikovich , , ; Grigoriev et al ., ; Tolmacheva et al ., ].…”

“…Currently, API technique is used as method to study the ionosphere and neutral atmosphere. Results of these studies and the theory of API formation and decay are summarized in the monograph [ Belikovich et al ., ] and papers [ Bakhmet ' eva et al ., ; Bakhmetieva and Belikovich , , ; Grigoriev et al ., ; Tolmacheva et al ., ]. APIs were observed at the heating facilities at Arecibo [ Feier et al ., ], High Power Auroral Stimulation (HIPAS) [ Djuth et al ., ], European Incoherent Scatter (EISCAT) [ Rietveld et al ., ; Rietveld and Goncharov , ; Vierinen et al ., ], and High Frequency Active Auroral Research Program (HAARP) [ Hysell et al ., ; Grach et al ., ].…”