Probing the Dynamic Ionosphere: A Multifaceted Approach

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More than just a beautiful sight, the aurora is the visible manifestation of massive electric currents that thread near-Earth space and inject billions of Watts of electrical power into our upper atmosphere. The aurora affects our atmosphere and possibly our climate, and provides a ringside view of fundamental plasma processes that pervade the universe. It can also pose a threat to technology in space and on the ground. ******Popular articles and even astronomy textbooks tend to give an oversimplified explanation of the aurora in terms of charged particles from the solar wind “captured” by Earth's magnetic field and channeled to the magnetic poles. In reality the connection between the solar wind and the aurora is more complex, and much more interesting. For example, auroral electrons are accelerated to energies 1000 times larger than those in the solar wind, a fact that cannot be explained by a magnetic field alone. Furthermore, the most intense auroras draw electrons from a source deep in the magnetosphere, with no direct access to the solar wind. Most importantly, the simple explanation misses the point that the aurora is fundamentally part of an electric circuit, powered by a magneto-hydrodynamic dynamo formed from the interaction of the fast-flowing solar wind with the geomagnetic field. ******This proposal is aimed at resolving key questions pertaining to formation of the aurora, and more generally to sources structure and variability of Earth's ionosphere by taking advantage of a rich and timely opportunity made possible by Canadian leadership in an unprecedented array of space and ground-based instrumentation. Foremost for this project are the Electric Field Instruments (EFIs) on the European Space Agency's Swarm satellites, launched in November 2013. These instruments were developed at the University of Calgary in collaboration with Canadian industrial partner COM DEV International (now Honeywell) and the Swedish Institute for Space Physics. Electric field estimates are derived from low-energy plasma measurements that include ion flow velocity, plasma density, and temperature. Combining these with state-of-the-art magnetic field measurements, Swarm is currently carrying out a precision, long-term, multi-point, pole-to-pole survey of the electrodynamic behavior and plasma properties of the ionosphere. Although Swarm itself has no direct measurements of auroral light nor the energized electrons that cause it, we are able to obtain this information separately through an array of white-light all-sky cameras deployed across the Canadian Arctic as part of the NASA/CSA THEMIS ground-based observatory chain, and soon through the new TREx (Transition Region Explorer) multi-wavelength array, both made possible through a collaboration with the auroral imaging group at the University of Calgary.