AMPERE polar cap boundaries
This study presents a new set of open-closed magnetic field line boundaries (OCBs) obtained from Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) magnetic perturbation data. AMPERE observations of field-aligned currents (FACs) are used to determine the location of the boundary between the Region 1 (R1) and Region 2 (R2) FAC systems. This current boundary is thought to typically lie a few degrees equatorward of the OCB, making it a good candidate for obtaining OCB locations. The AMPERE R1-R2 boundaries are compared to the Defense Meteorological Satellite Program Special Sensor J (DMSP SSJ) electron energy flux boundaries to test this hypothesis and determine the best estimate of the systematic offset between the R1-R2 boundary and the OCB as a function of magnetic local time. These calibrated boundaries, as well as OCBs obtained from the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) observations, are validated using simultaneous observations of the convection reversal boundary measured by DMSP. The validation shows that the OCBs from IMAGE and AMPERE may be used together in statistical studies, providing the basis of a long-term data set that can be used to separate observations originating inside and outside of the polar cap.
This research has been supported by the United States Chief of Naval Research (US CNR); the United Kingdom Research and Innovation (UKRI), British Antarctic Survey – Polar Science for Planet Earth Programme; the Air Force Office of Scientific Research (grant nos. FA9550-17-1-0258 and FA9559-16-1-0364); and the National Science Foundation, Office of Polar Programs (grant no. OPP-1836426).
CitationBurrell, A. G., Chisham, G., Milan, S. E., Kilcommons, L., Chen, Y.-J., Thomas, E. G., and Anderson, B.: AMPERE polar cap boundaries, Ann. Geophys., 38, 481–490, https://doi.org/10.5194/angeo-38-481-2020, 2020.
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