Modeling the effects of equatorial plasma bubbles on the oblique propagation of high-frequency electromagnetic waves

The ionosphere, as an essential component of the Earth’s space environment, contains free electrons that influence the amplitude and phase of radio signals. In the equatorial and low-latitude regions, plasma bubbles in the F region, manifested as electron density depletion, are observed frequently during the postsunset period. This phenomenon severely impacts the performance of modern electronic systems, such as short-wave communications and satellite navigation systems. In short-wave communication and target localization systems, the propagation mode of high-frequency electromagnetic waves in the ionosphere is typically oblique propagation. Therefore, studying the effects of equatorial plasma bubbles (EPB) on the oblique propagation characteristics of short waves is of significant engineering application importance. In this study, first, a model of plasma bubbles was used to produce equatorial plasma bubbles in the ionosphere. Then, a ray-tracing method was utilized to simulate the oblique propagation of radio waves in the ionosphere and synthesize oblique ionograms. Finally, the influence of EPB on the morphology of oblique ionograms was investigated, and the synthesized ionograms were compared with the measured oblique ionogram. Results showed that the features of the echoes such as satellite traces in the low working frequency band and diffuse echoes in the high working frequency band could be well reproduced in the simulated oblique ionograms, and that EPB could cause severe spread in both the group path and frequency of the high working frequency band of oblique ionograms, which was highly similar to the characteristics of spread F in the measured ionograms.