Preliminary Investigation of Solar Cycle 24 Storms and their Effects on SBAS Navigation

Seebany Datta-Barua, Gary S. Bust, Todd Walter, Geoff Crowley

Abstract:	Solar cycle 24 is in progress with significant solar activity beginning in 2011 and ongoing in 2012 prior to the anticipated peak in sunspots in 2013-14. We broadly review the major solar-induced geomagnetic storms of the current cycle that have been geoeffective in the American sector by surveying Kp and Dst geomagnetic indices for these periods. We summarize the WAAS Performance Analysis reports for events that affected WAAS. Focusing on the major October 24-25, 2011 storm, we examine WAAS operational system coverage for CONUS on the 25th. The timing of loss of coverage is coincident with the timing of Dst storm indication, which occurs at local nighttime in the American sector. A second loss of coverage occurs during the local daytime of 25 Oct. We compare this with the WAAS algorithm upgrade Release 3A performance. The upgrade improves on the nighttime loss of coverage slightly, but is much better able to maintain precision approach (PA) service in CONUS through the daytime of 25 Oct. To examine the nighttime ionosphere that led to the CONUSwide loss of PA, we combine data from multiple networks worldwide including IGS, LISN, and UNAVCO. With the Ionospheric Data Assimilation Four-Dimensional (IDA4D) tool, which uses three-dimensional variational data assimilation to map ionospheric densities globally, we generate total electron content (TEC) maps of the ionosphere on 24-25 Oct 2011. IDA4D is run in a low-resolution (3 x 3) global mode. We relate these TEC maps to WAAS availability maps for the time periods of interest. IDA4D is also at high-resolution (1 x 1) for Florida. The IDA4D electron density estimates are then fed to Estimating Model Parameters from Ionospheric Reverse Engineering (EMPIRE). EMPIRE deduces plasma velocities due to ionospheric dynamics, such as neutral winds and electric fields, from the time-evolving 3-dimensional images of ionospheric density. The IDA4D integrated electron densities show a nighttime co-rotating persistent plume extending from Florida west-northwest across central CONUS. Such an effect was observed during some storms of solar cycle 23, most notably in the extreme storm of Oc 2003. Horizontal drifts estimated by EMPIRE are shown to be northwestward, which may partly explain the plume’s duration of several hours through the night. We correlate the electron density distribution from IDA4D with ionospheric drivers from EMPIRE, the Dst, and the resulting availability of WAAS precision approach (LPV-200) service. In this way we provide a preliminary end-to-end view of a regionally geoeffective space weather storm from solar maximum 24.
Published in:	Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012) September 17 - 21, 2012 Nashville Convention Center, Nashville, Tennessee Nashville, TN
Pages:	2731 - 2741
Cite this article:	Datta-Barua, Seebany, Bust, Gary S., Walter, Todd, Crowley, Geoff, "Preliminary Investigation of Solar Cycle 24 Storms and their Effects on SBAS Navigation," Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012), Nashville, TN, September 2012, pp. 2731-2741.
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