Numerical simulation of oblique ionospheric heating by powerful radio waves

Abstract

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.

GLONASS Observation of Artificial Field‐Aligned Plasma Irregularities Near Magnetic Zenith During EISCAT HF Experiment

“…This time scale corresponds to the saturation time due to thermal self‐focusing instability (Kosch et al., 2007). Numerical simulation shows that the growth of large‐scale density perturbation in the scale of 10% requires 180 s after HF on (Liu et al., 2018).…”

“…Localized enhancement of electron density may be explained by suppression of recombination due to increased electron temperature or by the ionization by accelerated suprathermal electrons. Numerical simulation shows the electron density depletion associated with temperature enhancement at the reflection region (Gondarenko et al., 2006), which leads to the upper and lower region through the large‐scale thermal diffusion along the field line (Liu et al., 2018; Zhou et al., 2016). Indeed, in our experiment, the electron density increases both above and below the reflection height and a positive density deviation is observed by both incoherent scatter radar and GLONASS measurements.…”

“…In situ measurement showed that the density depletion near the reflection height associated with small‐scale FAI is structured in a scale of hundreds meters appearing in large groups with a radius of a few kilometers in the disturbed region (Kelley et al., 1995). The developed thermal pressure gradient can push the electrons along the magnetic field line (Liu et al., 2018; Zhou et al., 2016). Increased electron temperature or accelerated electrons can lead to an electron density enhancement at the upper/lower region along the field line.…”

Recent ionospheric investigations in China (2018–2019)

“…Liu MR et al (2018) investigated ionospheric heating by oblique incidence of powerful HF radio waves using three‐dimensional numerical simulations. They established a model to simulate three‐dimensional ionospheric heating by oblique incidence of powerful HF radio waves.…”

Effects of Earth's magnetic field variation on high frequency wave propagation in the ionosphere

“…Linked to ray paths through the ionosphere is the "spitze" phenomenon (Poeverlein, 1948), which occurs for the ordinary ray when the propagation is in the magnetic meridian for incident angles in the range between zero and a critical value that depends exclusively on the geomagnetic field intensity and inclination values (Davies, 1965;Budden, 1961). This critical angle, called spitze angle, is in general useful for ionospheric modification by powerful radio waves experiments, and specifically 65 ionospheric heating (Pedersen et al, 2003;Honary et al, 2011;Liu et al, 2018). According to Isham et al (2005), "the maximum topside backscattered power occurs neither at the Spitze angle nor at field-aligned, but somewhere between."…”