Abstract
<p><strong>Abstract.</strong> In this paper, we investigate the ionospheric heating by oblique incidence of powerful high-frequency (HF) radio waves using three-dimensional numerical simulations. The ionospheric electron density and temperature perturbations are examined by incorporating the ionospheric electron transport equations and ray-tracing algorithm. The energy distribution of oblique incidence heating waves in the ionosphere is calculated by the three-dimensional ray-tracing algorithm. The calculation takes into consideration the electric field of heating waves in the caustic region by the plane wave spectral integral method. The simulation results show that the ionospheric electron density and temperature can be disturbed by oblique incidence of powerful radio waves, especially in the caustic region of heating waves. The oblique ionospheric heating with wave incidence parallel and perpendicular to the geomagnetic field in the mid-latitude ionosphere is explored by simulations, results of which indicate that the ionospheric modulation is more effective when the heating wave propagates along the magnetic field line. Ionospheric density and temperature striations in the caustic region due to thermal self-focusing instability are demonstrated, as well as the time evolution of the corresponding fluctuation spectra.</p>
Highlights
Since the Luxembourg effect was discovered in the 1930s, the ionospheric modification by using powerful HF radio waves has been an important tool for investigating the physical processes of interactions between ionospheric plasma and electromagnetic waves
The simulation results demonstrated that the ionospheric electron density/temperature changes are generated by the vertical heating and the embedded large-scale field-aligned irregularities (FAIs) are induced by thermal self-focusing instability, which shows that the thermal process with diversity scales plays an important role in the ionospheric heating
Their simulation results demonstrate that the FAIs generated and developed due to the local heating show strong enhancement of electron temperature inside the depletions elongated along the magnetic field line
Summary
Since the Luxembourg effect was discovered in the 1930s, the ionospheric modification by using powerful HF radio waves has been an important tool for investigating the physical processes of interactions between ionospheric plasma and electromagnetic waves. M. Liu et al.: Numerical simulation of oblique ionospheric heating by powerful radio waves expected to produce evident changes in ionospheric electron density and temperature, the large-scale spatial disturbance of electron density structure in the F region can alter the propagation path of the heating waves and induce focusing/defocusing effects, which have been reported in many experiments (Hansen et al, 1990, 1992a). In the studies presented by Zhou et al (2016), the evolution of the large-scale ionospheric electron density and temperature modulation by powerful electromagnetic waves is investigated by a three-dimensional vertical heating model. The simulation results demonstrated that the ionospheric electron density/temperature changes are generated by the vertical heating and the embedded large-scale FAIs are induced by thermal self-focusing instability, which shows that the thermal process with diversity scales plays an important role in the ionospheric heating.
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