Multiple Phase Screen Modeling of HF Wave Field Scintillations Caused by the Irregularities in Inhomogeneous Media

Abstract

High frequency (HF) radio waves propagating through regions of ionospheric plasma irregularities exhibit random fluctuations in both amplitude and phase referred to as scintillations, which heavily influences the detection performance of HF sky‐wave radar and hybrid sky‐surface wave radar systems. In this paper, a numerical multiple phase screen model for HF sky‐wave propagation is developed, which can simulate the HF wave field scintillations caused by the irregularities in inhomogeneous media. In this model, the random phase changes due to irregularities and the diffraction effect due to phase mixing are considered separately and computed sequentially, where the phase change is numerically calculated using a geometric optical phase delay to allow for the consideration of horizontal electron density gradients. Utilizing the proposed model, we first simulate the observations of scintillation from the direct wave of the HF hybrid sky‐surface wave radar. The statistics of simulation and measured data, including power spectrum and scintillation indices on amplitude and phase, are considered to verify the effectiveness of the proposed model. Then, we analyze the effects of traveling ionospheric disturbances (TIDs) on the intensity of scintillation. The simulation indicates that the horizontal electron density gradients due to TIDs cause the fluctuation of the amplitude scintillation index S4.

Azimuth Resolution Improvement and Target Parameters Inversion for Distributed Shipborne High Frequency Hybrid Sky-Surface Wave Radar

“…Under the assumption of a quiet ionosphere, the ionosphere only causes the variation of the group-range, which ignores its effect on the phase of echo signals. However, the phase of the echo signals under non-stationary ionospheric conditions will be affected by a phase modulation and random perturbations [3,[41][42][43][44][45], so perturbation correction methods [5,57] are needed to improve the performance of algorithms. Moreover, ionospheric parameters vary during the day, year, and solar cycle, which affects variations in signal propagation in the ionosphere.…”

“…As mentioned earlier, it should be noted that Equation ( 12) is obtained in the case of a quiet ionosphere, such as quiet mid-latitude paths [37], and shipborne platforms with uniform linear motion, and it is assumed that the suppression of the sea clutter is completed. However, for the non-ideal cases, such as ionospheric disturbances and the six degree-of-freedom (DOF) motion of shipborne platforms, the model needs to be improved, which is beyond the scope of this paper and can be analyzed separately [41][42][43][44][45][46][47][48][49].…”

lensing from small-scale travelling ionospheric disturbances observed using lofar

“…The use of numerical phase screen models in the ionosphere has previously focused on anthropogenic radio sources, such as ground-or space-based radar systems and GNSS signals (e.g. Carrano et al, 2020;Ding et al, 2021;Hocke and Igarashi, 2003;Ludwig-Barbosa et al, 2019;Wang et al, 2014), meaning that care must be taken in defining the input spectrum of a natural source as considered here. As the source is incoherent, each angular component must be treated separately, to avoid the spurious phase relationships between the components that occur if they are combined into a single spectrum.…”

Polarization Characteristics Distortion for L-Band Fully Polarimetric Radar Subject to Magnetized Plasma Sheath

“…The idea of the phase screen method is first applied to simplify complex non-uniform structures by approximating with discrete uniform structures. Based on this, the piecewise integral method is used to analyze the propagation characteristics of radar waves in a non-uniform plasma sheath [27]. To date, the phase screen method has been utilized to analyze the impact of hypersonic turbulence on SAR imaging within the plasma sheath [28].…”