Analysis of Ionospheric Compressional Waves and Electron Density Oscillation During Storm Periods Using Swarm Observations

Using Swarm satellite observations, we aimed to examine compressional electromagnetic ion cyclotron (EMIC) waves and concurrent plasma density oscillations during storm periods (2014-2018). Compressional waves were accompanied by precipitated energetic proton fluxes, which can lead to increased electron density in the F-layer. Approximately one-third of compressional waves were accompanied by electron density (Ne) oscillations. The Ne oscillation occurred more frequently during stronger magnetic storms and with EMIC wave events of larger power density. The morning sector and South Atlantic Anomaly region revealed high occurrence rates of Ne oscillations. Its peak occurrence region showed a local time drift during the storm evolution. These variations with magnetic local time and storm phases are consistent with those of EMIC waves. Phases of the EMIC compressional waves and Ne oscillations exhibited a strong correlation. The phases of EMIC waves and Ne oscillations were linearly related, apart from a bias of similar to 17.5 degrees or 200.5 degrees. The relative amplitude ratio of most Ne oscillations to the compressional EMIC wave showed a strong correlation with the local Alfven velocity. When the Alfven velocity increased, the relative amplitude ratio also increased, and there appeared a saturation of the relative amplitude ratio at large Alfven velocity.