Observations of the Electrodynamical Ties Between Sporadic E and the Plasmasphere

A joint investigation was conducted of coherent backscatter radar observations of irregularities within the E and F regions and tomographic mapping of corotating plasmaspheric irregularities (CPIs) near Japan and the American northwest from June 2018. Within both areas, the amplitudes/detection rates for CPIs associated with ionospheric phase fronts aligned northwest-to-southeast peaked at night, predominantly premidnight. Likewise, the line-of-sight velocity dispersion measured within the E region from coherent backscatter in both areas peaked during the same time periods. Additionally, there were several instances of southwest propagating phase fronts within the E region backscatter data, with speeds similar to 100 m s(-1) and wavelengths similar to 300 km. Both the CPI amplitudes and E region velocity dispersions were typically larger near Japan. In both geographic areas, detections of sporadic E (E-S) were prevalent during all times, as is typical at midlatitudes in northern summer. Such southwestward propagating phase fronts have often been observed within summer nighttime E-S layers and have been tied to electrobuoyancy waves in the F region. Simulations of plane wave electric field disturbances within E-S layers with amplitudes constrained by the backscatter velocity dispersion measurements were able to reproduce the observed CPI properties. These simulated disturbances had smaller wavelengths (50 km) and speeds (20 m s(-1)) than those observed within the backscatter data but had similar oscillation periods. This may imply a population of smaller-scale wave-like disturbances that contribute significantly to the observed velocity dispersion but are too small to be resolved within the radar data.