Daytime F Region Echoes at Equatorial Ionization Anomaly Crest During Geomagnetic Quiet Period: Observations From Multi‐Instruments

Abstract

By using Qujing very high frequency radar (25.6°N, 103.7°E, magnetic latitude 16.1°N, magnetic longitude 177.0°E), daytime F region echoes were reported at equatorial ionization anomaly crest on 26 June 2020. Radar interferometry experiment was performed during the observation period. The observed results show that the spatial distributions of daytime F region echo pattern were about 150 km, 200 km, and 180 km in the zonal, meridional, and height extents, respectively. In addition, we observed a remarkable eastward drift of F region echoes with a mean velocity of about 50 m/s. To investigate the possible generation mechanism of daytime F region echoes, simultaneous occurrences of ionospheric disturbance and atmospheric gravity wave activities were presented by combining with the observations of ionosonde, global position system stations and FY‐4A satellite. The existence of gravity wave from the deep convective activities in the lower atmosphere was confirmed by using FY‐4A satellite measurements. The gravity wave signatures were also observed in the time series of virtual height deviations of sporadic E (dhES) and total electron content near the region where the F region echoes. We surmise that ionospheric disturbance in the F region could be excited during atmospheric gravity wave activities. Then the large‐scale ionospheric disturbance could further evolve into small‐scale irregularity producing radar echoes through the non‐linear cascade process.

Simulation of Es Layer Modulated by Nonlinear Kelvin–Helmholtz Instability

“…Based on the electrojet theory (Farley, 1963), the polarization electric field mechanism associated with Es layer has been proposed (Haldoupis et al, 1996a;Kagan & Kelley, 1998;Liu, Deng, et al, 2022, 2022bMaruyama et al, 2000;Rosado-Roman et al, 1999;Saito et al, 2006;Shalimov et al, 1998;Tsunoda et al, 1994;Woodman et al, 1991). Simulations reveal that QP echoes associated with FAIs are related to the horizontal structure in the Es layer and that the polarization electric fields are induced by the ambient electric field, neutral wind, or the gravity waves (Haldoupis & Pancheva, 2006;Yokoyama et al, 2003Yokoyama et al, , 2004.…”