Studies of the ionospheric turbulence excited by the fourth gyroharmonic at HAARP

Abstract

A study is presented of artificial ionospheric turbulence (AIT) induced by HF heating at High Frequency Active Auroral Research Program (HAARP) using frequencies close to the fourth electron gyroharmonic, in a broad range of radiated powers and using a number of different diagnostics. The diagnostics include GPS scintillations, ground‐based stimulated electromagnetic emission (SEE), the HAARP ionosonde, Kodiak radar, and signals received at the Ukrainian Antarctic Station (UAS). The latter allowed analysis of waves scattered by the AIT into the ionospheric waveguide along Earth's terminator, 15.6 mm from the HAARP facility. For the first time, the amplitudes of two prominent SEE features, the downshifted maximum and broad upshifted maximum, were observed to saturate at ~50% of the maximum HAARP effective radiated power. Nonlinear effects in slant total electron content, SEE, and signals received at UAS at different transmitted frequencies and intensities of the pump wave were observed. The correlations between the data from different detectors demonstrate that the scattered waves reach UAS by the waveguide along the Earth's terminator, and that they were injected into the waveguide by scattering off of artificial striations produced by AIT above HAARP, rather than via direct injection from sidelobe radiation.

Artificial Ionospheric GPS Phase Scintillation Excited During High‐Power Radiowave Modulation of the Ionosphere

“…The signature of excited EB/UH mode associated with the four‐wave decay instability manifests itself in BUM feature in the WSEE spectrum. According to the past observations (Milikh et al, ; Najmi et al, , ), correlation of BUM spectral line in the WSEE spectrum and STEC fluctuations/GPS scintillation in the experimental observation during pump heating at HAARP shows that the physical processes involved in the generation of both phenomenon are similar.…”

“…The observed weak GPS scintillations in the absence of four‐wave decay instability and SSS (f 0 > 5.82 MHz) is attributed to the decameter‐scale irregularities within the Fresnel zone. A correlation with the heating cycle and HAARP pump power is observed in the HF signals received at the UAS (Najmi et al, ). The agreement between the amplitude DM in WSEE spectra and SNR of the received signal at the UAS is observed, which validates the presence of the decameter‐scale FAI, and scattering of HF pump waves from into the Earth‐ionosphere waveguide is responsible for the received signal in Antarctica along the ionospheric channel (Najmi et al, ; Zalizovski et al, ).…”

“…Time series of the received signal (signal‐to‐noise ratio, SNR) at the UAS during the heating experiment carried out on 7 June was observed (Najmi et al, ). Zalizovski et al () and Najmi et al () have reported the detection of HF signal transmitted from HAARP/European Incoherent Scatter Scientific Association at the UAS, which is attributed to the coherent scattering of the transmitted HF signal by the artificial ionospheric irregularities (artificial FAIs). A comparison between the amplitude of the HF signal received at the UAS and WSEE spectral lines by Najmi et al () shows correlation between the UAS receive signal SNR and the WSEE strength (see their Figures 8–10).…”

“…Generation of artificial FAIs in the range from tens of meters up to a few kilometers has been predicted in theory and observed in experiments (Dhillon & Robinson, ; Gondarenko et al, ; Gurevich, ). Recent observations have shown that the High Frequency Active Auroral Research Program (HAARP) signal can be detected in Antarctica 15.6 Mm from the HAARP facility as a result of scattered waves by the artificial striations into the ionospheric waveguide along the Earth's magnetic field (Najmi et al, ).…”

Properties of the Stimulated Electromagnetic Emissions During the Inclined High‐Frequency Pumping of the Ionosphere Near the Fourth Electron Gyroharmonic at the High‐Frequency Active Auroral Research Program Facility

“…Many phenomena in the HF-pumped volume such as artificial airglow, descending artificial ionization layers, and pump-induced plasma irregularities, exhibit dependence on the angle of incidence, α, between the pump beam and the vertical (Grach et al, 2007(Grach et al, , 2012(Grach et al, , 2018Kosch et al, 2004Kosch et al, , 2014Mishin et al, 2016;Najmi et al, 2015;Pedersen & Carlson, 2001;Pedersen et al, 2009;Rietveld et al, 2003;Sergeev et al, 2013;Yampolski et al, 2019). Understanding these phenomena requires a systematic study of the SEE properties' α dependence, particularly near gyroharmonics.…”