New pathways for EMIC wave propagation within the ionosphere: SWARM observations and modelling

Electromagnetic ion cyclotron (EMIC) waves are important because of their essential role in reducing the amount of radiation in the Earth's radiation belts under geomagnetic storm conditions. In this presentation, we show results from a new simulation model of EMIC waves and compare them with SWARM satellite data and ground-based observations [I. P. Pakhotin et al., Geophys. Res. Lett., 2022, doi:10.1029/2022GL098249]. The EMIC wave model is a first-of-a-kind in accounting for wave propagation in the magnetosphere and a realistic ionosphere specified using the IRI and MSIS empirical models. The inclusion of a realistic ionosphere in the model enables new pathways to the upper atmosphere to be identified, which is crucial for understanding the waves detected on the ground. We show using a model-data comparison that EMIC wave energy is reflected at different locations in the ionosphere toward the equator to form standing waves. This is a new resonance phenomenoncreated by interference of waves that produces an amplitude peak in the upper atmosphere at lower latitudes, far from the location of the initial source. Understanding such pathways is crucial for correctly diagnosing the location of EMIC wave populations in space, and assessing their role in radiation belt loss.