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Title: AMPERE polar cap boundaries
Abstract. The high-latitude atmosphere is a dynamic region with processes that respond to forcing from the Sun, magnetosphere, neutral atmosphere, andionosphere. Historically, the dominance of magnetosphere–ionosphere interactions has motivated upper atmospheric studies to use magneticcoordinates when examining magnetosphere–ionosphere–thermosphere coupling processes. However, there are significant differences between thedominant interactions within the polar cap, auroral oval, and equatorward of the auroral oval. Organising data relative to these boundaries hasbeen shown to improve climatological and statistical studies, but the process of doing so is complicated by the shifting nature of the auroral ovaland the difficulty in measuring its poleward and equatorward boundaries. This study presents a new set of open–closed magnetic field line boundaries (OCBs) obtained from Active Magnetosphere and Planetary ElectrodynamicsResponse Experiment (AMPERE) magnetic perturbation data. AMPERE observations of field-aligned currents (FACs) are used to determine the location ofthe boundary between the Region 1 (R1) and Region 2 (R2) FAC systems. This current boundary is thought to typically lie a few degrees equatorwardof the OCB, making it a good candidate for obtaining OCB locations. The AMPERE R1–R2 boundaries are compared to the Defense MeteorologicalSatellite Program Special Sensor J (DMSP SSJ) electron energy flux boundaries to test this hypothesis and determine the best estimate of thesystematic offset between the R1–R2 boundary and the OCB as a function of magnetic local time. These calibrated boundaries, as well as OCBsobtained from the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) observations, are validated using simultaneous observations of theconvection reversal boundary measured by DMSP. The validation shows that the OCBs from IMAGE and AMPERE may be used together in statisticalstudies, providing the basis of a long-term data set that can be used to separate observations originating inside and outside of the polar cap.  more » « less
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Author(s) / Creator(s):
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Date Published:
Journal Name:
Annales Geophysicae
Page Range / eLocation ID:
481 to 490
Medium: X
Sponsoring Org:
National Science Foundation
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