Numerical simulation studies on the broad upshifted maximum of ionospheric stimulated electromagnetic emission

Abstract

Abstract. Stimulated electromagnetic emission (SEE) produced by interactions ofhigh-power radio waves with the Earth's ionosphere is currently a topic of significant interest in ionospheric modification physics. SEE is believed to be produced by nonlinear wave-wave interactions involving the electromagnetic and electrostatic plasma waves in the altitude region where the pump wave frequency is near the upper hybrid resonance frequency. The most prominent upshifted feature in the SEE spectrum is the broad upshifted maximum (BUM). From characteristics of this feature, a four-wave parametric decay process has been proposed as a viable mechanism for its production. The object of this work is to (1) investigate the early time nonlinear development of the four-wave decay instability by using theoretical and numerical simulation models, (2) study the variation of the four-wave decay instability spectral features for a wide range of plasma and pump wave parameters, and (3) access its possible role in the production of the BUM spectral feature. Results of this investigation show that there is good agreement between predictions of the proposed theoretical model and the numerical simulation experiments.The simulation electric field power spectrum exhibits many of the important features of the experimental observations. The numerical simulation results show that consideration of the full nonlinear development of the four-wave parametric instability is crucial in providing insight into the asymmetric nature of the wave frequency spectrum observed during the experiments.

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

“…Linear dependence of the BUM peak frequency shift Δ f BUM on f 0 (equation ) provides a method to estimate effective BUM generation altitude for each sweep cycle, assuming UH waves responsible for the BUM generation are excited by a four‐wave interaction: (two quanta of UH waves at frequency f 0 produce one UH quantum at f BUM and one Bernstein (B) wave quantum at f b ≈ 4 f c ). BUM generation via a four‐wave interaction was suggested by Leyser et al () and considered by Huang and Kuo (), Vas'kov and Ryabova (), Xi and Scales () and Fu and Scales (). Rewriting equations and as where h BUM is the effective source altitude of BUM and f * is the frequency f 0 for which equation implies Δ f BUM = 0, we obtain …”

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

“…The dispersion relation for decay of the pump wave ( ω 0 ) into an EB wave ( ω eB ) with downshifted frequency, UH ω uh with upshifted frequency, and plasma oscillation near ω lh used in this study is given by (Huang & Kuo, ; Hussein & Scales, ; Xi & Scales, ):…”

“…A variety of parameters such as pump power, frequency offset relative to the fourth gyrofrequency, and angle of the pump field relative to the geomagnetic field are considered. Computational results from the one‐dimensional PIC model previously developed by Xi and Scales () are used to interpret the behavior of EB and UH waves excited through four‐wave decay instability in the nonlinear regime. The linear growth and damping of EB/UH waves obtained using both the linear growth rate and computational model are used to interpret the data collected at HAARP (WSEE and STEC) and the Ukrainian Antarctic Station (UAS) near South Pole.…”

Electrostatic electron cyclotron instabilities near the upper hybrid layer due to electron ring distributions

“…Experimental observations [46][47][48] show that the peak frequency BUM ω approximately obeys n BUM c e 0 0 ω ω ω ω − = − when the transmitted frequency 0 ω is above one of the electron cyclotron harmonics, n ce 0 ω ω > . An alternative model for the broad upshifted maximum is a 4-wave parametric decay scenario [49,50] involving the transmitted pump wave, the upper hybrid and nearest lower electron Bernstein branch, and the lower hybrid waves, which seems to account for the observed frequency upshift.…”