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

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 latter of which performs better in isolating the fine spatial structure. The GNSS TEC maps indicate that the Es episode is accompanied by a primary east-west elongated (up to similar to 180 km) southward migrating TEC striation with a speed of similar to 90 m/s and similar to 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 in the primary striation gradually increases from the frontal leading edge but abruptly drops in the trailing edge. MAI-based TEC map confirms multiple TEC striations as previously suggested in GNSS TEC time-series, which are reminiscent of the quasi-periodic (QP) echoes in nighttime Es detected by the middle and upper atmosphere (MU) radar, but the periodicity is not as clear as that observed by MU radar. The Kelvin-Helmholtz (KH) instabilities around the wind shear of neutral winds could be responsible for the QP TEC striations.