E-Region Field-Aligned Irregularities in the Middle of a Solar Eclipse Observed by a Bistatic Radar

Abstract

The Wuhan Ionospheric Oblique Backscatter Sounding System (WIOBSS) was applied as a bistatic radar to record the ionospheric E-region responses to a solar eclipse on 22 July 2009. The transmitter was located in Wuhan and the receiver was located in Huaian. The receiver observed anomalous echoes with larger Doppler shifts at the farther ranges compared with the echoes reflected by Es. According to the simulated ray propagation paths of the reflected and scattered waves, we considered that the anomalous echoes were scattered by E-region field-aligned irregularities (FAIs). The locations of the FAIs recorded by the WIOBSS were estimated with the International Geomagnetic Reference Field (IGRF) and the observed propagation parameters. These irregularities occurred at around the eclipse maximum and lasted for ~20–40 min. The steep plasma density gradient induced by the fast drop photo ionization under the lunar shadow was beneficial to the occurrence of gradient drift instability to generate the FAIs. They were different from the gravity wave-induced irregularities occurring in the recovery phase of the solar eclipse.

Intermediate Descending Layers Emerged Simultaneously in Five Different Locations During the Solar Eclipse on 21 June 2020

“…In addition, the supersonic movement of the moon's shadow in the ozone layer forms bow and gravity waves (e.g., Chimonas, 1970; Chimonas & Hines, 1971; Fritts & Luo, 1993; Zhang et al., 2017). The upward propagating gravity waves will have significant impact on all layers of ionosphere (e.g., Brahmanandam et al., 2013; Chen et al., 2015a; Lin et al., 2018; Paulino et al., 2020; Qiao et al., 2022; Thampi et al., 2010).…”

Ionospheric Total Electron Content and Scintillation Variations over Uzbekistan and China GPS stations during the Annular Solar Eclipse on 21 June 2020

“…The processes described above lead to the formation of plasma, which in turn chemically reacts with neutrals, disperse under the influence of gravity and pressure gradients, and is transported by neutral winds and electric fields under the influence of a magnetic field. It is found in [25] that anomalous echoes were propagated by field-aligned irregularities (FAIs) in the E-region, according to the simulated ray propagation paths of the reflected and scattered waves.…”