This INSPIRE award is partially funded by the Aeronomy and Magnetospheric Physics Programs in the Division of Atmospheric and Geospace Sciences in the Directorate for Geoscience, and the Earthscope Program in the Division of Earth Sciences in the Directorate for Geoscience.
The investigators will develop a self-consistent data-fusion algorithm that will simultaneously image the ground conductivity and ionospheric parameters based on magnetic field measurements and incoherent scatter radar measurements. The solar wind, magnetosphere, ionosphere, and atmosphere are coupled to Earth?s crust and mantle through electromagnetic induction, with geomagnetically induced currents (GICs) deep into the Earth. However, current assumptions and simplifications limit the interpretation of observations. Ionospheric currents are derived from ground-level magnetic perturbations without knowledge of the conductivity in the crust and mantle. Conversely, variations in conductivity of the crust and mantle assume that the ionosphere radiates a plane electromagnetic wave that drives currents through the varied ground-conductivity distribution. The source-strength is factored out of the analysis by forming the impedance from the magnetic and electric fields measured at ground level. The apparently inconsistent assumptions have been reconciled through statistical methods, but the effects of these assumptions are unknown. Near Fairbanks, under the auroral oval, is a multibeam incoherent scatter radar (Poker Flat Incoherent Scatter Radar (PFISR), with a multispectral all sky imager (ASI), and an imaging Fabry Perot interferometer. The National Geoelectromagnetic Facility (NGF) is a repository of magnetotelluric (MT) sensors that will include EarthScope?s Transportable Array to be deployed in Alaska. The combined data sets will allow the first testing of the fundamental paradigm concerning the source of ground-electromagnetic perturbations---a paradigm that has been challenged by a growing number of controversial papers identifying electromagnetic precursors to earthquakes, and that does not normally account for magnetic permeability. This fundamental paradigm also governs the GIC hazard, which, for the first time, will be analyzed with full knowledge of the ground conductivity and ionospheric current. The data-fusion algorithm to be developed will numerically solve the geoelectromagnetic induction problem and determine if the full suite of ground and ionospheric measurements can be rendered consistent, and with what accuracy. Any deviations will be investigated and their physical cause sought, thereby opening the door to new discoveries. Assuming that any inconsistencies can be resolved, the data will be fused to produce time-evolving three-dimensional images of auroral arcs, including the full three-dimensional current system that connects them to the magnetosphere through field-aligned currents. The first three-dimensional view of the electrical conductivity structure of the Alaskan lithosphere and upper mantle will also be produced, along with a two-dimensional transect of the Alaska margin, through the cordillera, and into cratonic North America beyond. The scientific results will guide development of an empirical model for the GIC hazard by identifying the needed descriptors of ground conductivity and geomagnetic activity. A postdoc and a graduate student from a traditionally underrepresented group will be trained in interdisciplinary research through their involvement with the project.
