Observations of the Electrodynamical Ties Between Sporadic E and the Plasmasphere

Abstract

Abstract 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 ∼100 m s−1 and wavelengths ∼300 km. Both the CPI amplitudes and E region velocity dispersions were typically larger near Japan. In both geographic areas, detections of sporadic E (ES) 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 ES layers and have been tied to electrobuoyancy waves in the F region. Simulations of plane wave electric field disturbances within ES 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.

Keywords

• sporadic E
• plasmasphere
• ionospheric disturbances
• ionosphere/plasmasphere coupling