Mapping the Polar Ionospheric Conductivities

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AbstractThe proposed activities explore creative and potentially transformative concepts to solve the fundamental problem of obtaining adequate conductivity maps in the polar region. This information is a missing link in our knowledge of magnetosphere-ionosphere coupling, which is hindering progress on this frontier. The proposed effort, which lays the groundwork for follow-on global modeling studies in the community, has the potential to significantly advance knowledge possibly even triggering a breakthrough in our understanding of Geospace electrodynamic coupling. The proposers plan to create a state-of-the-art empirical model of height-integrated electrical conductivities in the polar region by taking advantage of large datasets of magnetic field, electric field, and electric current measurements from recent and ongoing satellite missions and ground-based instrumentation. A new feature of the empirical model will be the ability to produce, for the first time, height-integrated electrical conductivity patterns as a function of solar EUV irradiance, the tilt of the Earth's magnetic dipole with respect to the Sun and the interplanetary magnetic field orientation - all of which are known to organize the spatial and temporal behavior of the conductivity as well as its magnitude. This is particularly important because ionospheric conductivity makes possible the closure through the upper atmosphere of currents that are generated by the interaction between the magnetosphere and the solar wind. It is also a key factor in determining how energy from these currents is deposited. Despite the critical role of the conductivity in driving the behavior of Geospace, it is still one of the most poorly known quantities because direct measurements are extremely difficult to make and direct observations of its global features have not yet been possible. The project provides training for a graduate student thus contributing to the future scientific workforce. The advances in knowledge about coupling within the Geospace system will likely lead to improved models and ultimately to better space weather predictions of value to society. The method for deriving ionospheric height-integrated conductivity requires electric fields supplied by an existing empirical model (which will be improved), divergence-free currents obtained from inversion of ground-based magnetometer data and curl-free currents obtained from satellite magnetometers. The curl-free current component is essentially the closing current through the ionosphere for magnetospheric field-aligned currents. If field lines are approximately vertical as in the polar regions, the current loop formed by the field-aligned and curl-free current produces no magnetic signature at the ground; hence the need for satellite observations of the magnetic field signature of the curl-free current. If the ionospheric conductivity is uniform, the curl-free current is the Pedersen current and the divergence-free current is essentially the Hall current, which can be detected through magnetic field perturbations observed on the ground.