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Abstract:
The Earth's ionosphere is home to numerous electric current systems driven by the global wind dynamo, gravity, pressure gradients, and coupling to the magnetosphere. Each of these current systems exhibits rich and complex structure on a wide range of both temporal and spatial scales. Improved understanding of the ionospheric current system enables us to predict the effects of space weather events, interpret magnetic field observations on ground and in space, and probe the conductivity structures of the deep Earth interior.The work we describe here is a simple data assimilation method which focuses on modeling the ionospheric currents in the diurnal frequency band. We utilize a one year TIEGCM simulation to construct a set of spatial modes which capture the salient 3D structures of the major ionospheric current systems. These spatial modes are then combined with a set of temporal modes derived from the ground observatory network over a 20 year time frame, in order to build a time-continuous 3D model of the global ionospheric current system in the diurnal variation band. This is, in effect, a 4D model of the ionospheric currents and their associated magnetic fields spanning two decades. We will report on the methodology used to build our model, as well as the main features of the model. We will also discuss possible extensions of our method to other frequency bands, in order to capture, for example, higher frequency variations which could occur during geomagnetic storms.
