Monitoring the Auroral Oval with GPS and Applications to WAAS

Peter J. Stewart and Richard B. Langley

Abstract:	Mitigation of ionospheric effects in and near the auroral zone is a challenge facing GPS users and service providers in the Canadian north, not the least of which are those promoting augmentations to GPS navigation such as the Wide Area Augmentation System (WAAS). One of the parameters of interest is the location of the auroral oval, the location and extent of which varies with solar and geomagnetic activity. As solar maximum draws ever closer, so periods of enhanced geomagnetic activity will become more frequent, and, consequently, the effect of the auroral ionosphere will become more prevalent at lower latitudes. Using a number of permanent dual frequency GPS receivers, the location of the auroral oval and its dynamics can be tracked by assuming that the level of ionospheric scintillation will be significantly higher for satellite-receiver paths traversing the oval. Identification of a marked decrease in background ionization will allow estimation of the auroral trough, an area of relatively low ionization found at the equatorward boundary of the oval. Comparison with empirical models of auroral location, such as the Feldstein ovals, provides validation of these results. We have tested this technique using data from 72 GPS receivers of the International GPS Service and the Continuously Operating Reference System, located north of 45° latitude for two days in May and June 1999 – one when the geomagnetic field was disturbed and one when it was quiet. The results of our initial tests are promising as they show reasonable agreement with both an empirical model and with a satellite-based statistical image. Enhancement of this technique should allow real time monitoring of the location and extent of the auroral oval, and provide additional information to the WAAS ionospheric message creation process.
Published in:	Proceedings of the 55th Annual Meeting of The Institute of Navigation (1999) June 27 - 30, 1999 Royal Sonesta Hotel Cambridge, MA
Pages:	379 - 385
Cite this article:	Stewart, Peter J., Langley, Richard B., "Monitoring the Auroral Oval with GPS and Applications to WAAS," Proceedings of the 55th Annual Meeting of The Institute of Navigation (1999), Cambridge, MA, June 1999, pp. 379-385.
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