SIEMIC: Swarm Investigation of the Energetics of Magnetosphere-Ionosphere Coupling

Living Planet Fellowship research project carried out by Ivan Pakhotin.

Ivan’s recent published work in magnetosphere-ionosphere coupling (MIC) using the unprecedented Swarm dataset has revealed that Alfven waves play a key role in MIC dynamics, with small scales carrying very significant amounts of energy. His recent preliminary work has further indicated that in fact most of the Poynting flux carried from the magnetosphere into the ionosphere appears to be carried by small-scale and mesoscale electromagnetic disturbances. This is in contrast to the state-of-the-art in the community, where low-pass filtering methods are routinely used to deliberately attenuate small and mesoscale FACs in an attempt to remove Alfven wave influence. This systematic exclusion of smaller scales leads to chronic underestimations of the energetics of MIC, which translates into uncertainty in the estimations of Joule heating when calculating magnetosphere-ionosphere-thermosphere (MIT) energy transport. Indeed modern MIT models have been found to contain significant uncertainties, particularly in the area of Joule heating and Poynting flux, which is hampering modelling efforts to establish the energy budget for the MIT system for space weather forecasting. 

 This project is a direct continuation of Ivan’s latest work, aiming to answer a single question: how much energy flows from the magnetosphere to the ionosphere at which scales into each hemisphere? His preliminary research has shown that, not only are Alfven waves and small scales extremely important for the energetics of MIC, but also it appears that energy input into the ionosphere may not be symmetric across hemispheres. A statistical study using Swarm electric and magnetic field data has shown consistently higher Poynting flux energy flow on the sunlit hemisphere if the spacecraft is in noon-midnight orbit. This contradicts the hypothesis that the ionosphere is a passive load where the only changes are due to conductivity differences. The interhemispheric asymmetry has been alluded to in recent modelling papers, but to the best of Ivan’s knowledge there has not been a thorough statistical study on this based on spacecraft observations. Such a result would be a significant milestone in understanding MIT energy transfer as it would elucidate the physical nature of key processes which as of now are not well understood. The improved energy calculations considering smaller scales will serve as a valuable input to ionosphere-thermosphere models and studies, and will facilitate high-quality research in that field.