Fine structure of a daytime mid-latitude sporadic-E revealed by GNSS TEC, InSAR, and MAI

Abstract

Abstract Combining the total electron content (TEC) data from two nationwide Global Navigation Satellite System (GNSS) networks in Japan with the L-band synthetic aperture radar (SAR) data, we reveal the fine spatial and temporal structure of a daytime sporadic-E (Es) episode in Shikoku, Japan. The snapshot of the Es is derived not only from interferometric SAR (InSAR) but also from multiple aperture interferometry (MAI). The Es episode is accompanied by east-west elongated (up to ~ 180 km) multiple southward migrating TEC striations with a speed of ~ 90 m/s and ~ 10–20 km widths in the north-south direction. As previously suggested by the GNSS TEC time series, the present InSAR and MAI data independently confirm that electron density gradually increases from the frontal leading edge but abruptly drops in the trailing edge. The asymmetric electron density distribution is consistent with a previous study but requires further clarifications that can account for the occurrence in the daytime. The multiple TEC striations are reminiscent of the quasi-periodic (QP) echoes in nighttime Es detected by the Middle and Upper Atmosphere (MU) radar. Still, no vertically extended anomalies are suggested in the present daytime Es. The Kelvin-Helmholtz instabilities around the wind shear of neutral winds could be responsible for the QP TEC striations.