M-I Coupling: Global Scale Imaging of High Latitude Poynting Flux

Johns Hopkins University, Baltimore MD

Investigators

Abstract

The investigators will use a new technique to evaluate the global-scale distribution of Poynting flux directly from the cross product of the electric field, E, with the magnetic perturbation intensity, b. The principal means by which energy is transported from the magnetosphere to the ionosphere is by Poynting flux and particle precipitation in the high latitude polar regions. Although the Poynting flux accounts for more energy, it is the least well characterized. Except for long-term statistical studies, evaluations of the global distribution of electromagnetic energy deposition in the high latitude ionosphere depend on statistical models of ionospheric conductivity. The magnetic perturbations in this study are derived from Iridium engineering magnetometer data and the electric field is derived from coherent ionospheric scatter radars of the SuperDARN system. By this method, the investigators will evaluate the global scale Poynting flux directly on time scales of about one hour with a resolution of 2 in latitude and two hours in longitude. The overarching scientific goal of this work is to characterize the role of high latitude Poynting flux in large-scale magnetosphere-ionosphere coupling. Results to date indicate that the regions of Poynting flux vary dramatically from case to case, possibly reflecting the influence of imposed solar wind conditions. The most intense Poynting flux is often concentrated in zones at auroral latitudes. In addition, the net Poynting flux over the polar cap accounts for roughly one third of the total. These results pose several issues that will be addressed. To accomplish this, the investigators will (1) Determine the partitioning of energy flux between electromagnetic and particle energy flux; (2) Identify thermospheric responses to regions of intense Poynting flux; (3) Compare the global distributions of Poynting flux with in-situ satellite determinations and incoherent scatter radar results; and (4) Investigate the influence of the neutral wind dynamo. The study will involve collaborative studies with other researchers. Comparison with results on IT dynamics obtained using other assets, particularly incoherent scatter radars is an integral component of the research. Another important element is the inter-comparison of products derived with the Iridium/SuperDARN data with other techniques including in-situ estimates of Poynting flux from DMSP satellites and smaller scale estimates of thermospheric properties and thermosphere/ionosphere response from other resources including incoherent scatter radars.