High-Resolution Poynting Flux Statistics from the Swarm Mission: What are we missing?

Electromagnetic energy transfer between Earth's magnetosphere and upper atmosphere at polar latitudes, the Poynting flux, is thought to be significantly underestimated in many studies. This underestimation mainly stems from the inability to capture small-scale spatio-temporal variability in the ionospheric electric field, as many instruments (both ground and satellite-based) sample too coarsely to observe Alfvénic frequencies of variability.

In this study, we use high-resolution electric field measurements from the Swarm satellite constellation to calculate Poynting fluxes at sub-kilometre scales. We compare these Poynting fluxes statistically to those calculated at a range of larger spatial scales (5km-1000km), showing that there is an underestimation of several tens of percent when comparing the high-res data to scales comparable with other commonly used instruments. Our results imply that small-scale electric field variability at Alfvénic frequencies is vital to accurately estimating the magnetosphere-ionosphere-thermosphere energy budget.