Kinrade, Joe and Badman, Sarah and Wu, Siyuan and Paranicas, Chris and Jackman, Caitriona and Clare, Leah and Louis, Corentin K. (2026) Coincident ENA and narrowband radio emissions as diagnostics of inward plasma transport at Saturn. Other. ESS Open Archive.
Full text not available from this repository.Abstract
Saturn’s kilometric radiation (SKR) and Energetic Neutral Atom (ENA) emissions are important diagnostics of the planet's magnetospheric dynamics, intensifying during global plasma injections and displaying characteristic planetary periodicity. Related to the SKR emissions are myriametric narrowband radio emissions that typically appear in the hours following SKR intensification. While these narrowband emissions (centered on frequencies around 5 and 20 kHz) have been associated with ENA signatures at evening local times (LT), the radial dependence of this relationship remains untested. Narrowband radio sources are thought to be triggered by temperature and density gradients at the inner edge of the Enceladus plasma torus. In this study, we use ENA keograms separated by radial distance (inner, middle, and outer magnetosphere) to quantify the timing of narrowband 'bursts' relative to ENA intensity. Additionally, we analyze both ENA and radio emissions in the co-rotating planetary frame to compare their rotational modulation. Our results show that 5 kHz bursts correlate most strongly with ENA enhancements rotating through the dusk-midnight sector in the inner magnetosphere. The 20 kHz band shows a weaker correlation and occurs slightly later. Specifically, 5 kHz bursts lead 20 kHz bursts by ~2–2.5 hours LT, consistent with a phase-locked relationship. These findings suggest that narrowband emission is triggered by a spatially dependent sequence: injected plasma drives the necessary anisotropy as it reaches the cooler inner magnetosphere beyond dusk. This provides a clearer picture of how global injection events influence Saturn’s internal plasma environment.