A Statistical Analysis of Auroral-Enhanced Plasma Lines Observed by EISCAT During One Solar Cycle

Abstract

Enhanced plasma lines (PLs) obtained from incoherent scatter radars can be utilized to estimate multiple parameters of the ionosphere. The occurrence rates of these PLs, intensified by auroral precipitations, depend on the magnetic local time (MLT) according to the source regions of the precipitated electrons. To comprehensively understand how both nightside and dayside PLs respond to the solar-wind-magnetosphere-ionosphere coupling interactions, we present the first-ever 11-year statistical analysis of PLs data. This analysis is based on the European Incoherent Scatter Scientific Association (EISCAT) incoherent scatter radar data set, spanning from 2009 to 2019. Our statistical analysis reveals distinctive characteristics in the behavior of enhanced PLs. The occurrence rates of PL enhancements in the E-region peak during nighttime (19:00–07:00 MLT), aligning with the activity of secondary electrons from the magnetotail, while in the F-region peaks occur during daytime (07:00–19:00 MLT), consistent with electron beams from the cusp. A clear seasonal preference emerges, with higher occurrence rates of PL enhancements in the E-region during winter and in the F-region during summer. This observation may be attributed to heightened auroral activity during equinoctial months. Additionally, the PL enhancements demonstrate a correlation with intervals of heightened solar-geomagnetic activity, providing further evidence for a robust connection to auroral precipitation. These findings offer valuable insights into the excitation mechanisms of enhanced PLs and present a novel tool for advancing research in particle precipitation.