A New DMSP Magnetometer & Auroral Boundary Dataset and Estimates of Field Aligned Currents in Dynamic Auroral Boundary Coordinates.

We have developed a method for reprocessing the multi-decadal, multi-spacecraft Defense Meteorological Satellite Program Magnetometer (DMSP SSM) dataset and have applied it to fifteen spacecraft-years of data (DMSP Flight 16-18, 2010-2014). This Level-2 dataset improves on other available SSM datasets with recalculated spacecraft locations and magnetic perturbations, artifact signal removal, representations of the observations in geomagnetic coordinates, and in-situ auroral boundaries. Spacecraft locations have been recalculated using ground-tracking information. Magnetic perturbations (measured field minus modeled main-field) are recomputed. The updated locations ensure the appropriate model field is used. We characterize and remove a slow-varying signal in the magnetic field measurements. This signal is a combination of ring current and measurement artifacts. A final artifact remains after processing: step-discontinuities in the baseline caused by activation/deactivation of spacecraft electronics. Using coincident data from the DMSP precipitating electrons and ions instrument (SSJ4/5), we detect the in-situ auroral boundaries with an improvement to the Redmon et al. [2010] algorithm. We embed the location of the aurora and an accompanying figure of merit in the Level-2 SSM data product. Finally, we demonstrate the potential of this new dataset by estimating field-aligned current (FAC) density using the Minimum Variance Analysis (MVA) technique. The FAC estimates are then expressed in dynamic auroral boundary coordinates using the SSJ-derived boundaries, demonstrating a dawn-dusk asymmetry in average FAC location relative to the equatorward edge of the aurora. The new SSM dataset is now available in several public repositories.