Size, shape, orientation, speed, and duration of GPS equatorial anomaly scintillations

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Abstract

[1] GPS L1 C/A signal scintillation data were collected at the equatorial anomaly over a period of three months using five receivers spaced on magnetic east-west and north-south axes to examine the speed, orientation, shape, width, and duration of GPS scintillation fade patterns. The nighttime speeds were primarily eastward in the range of 100–200 m/s with a significant spread to both larger values and negative (westward) values as expected, given the known behavior of ionospheric drifts and GPS signal path movement. The characteristic velocity was found to be small so that the true velocity was equal to the apparent velocity to a very good approximation. The orientation of the scintillation fade patterns was organized by a simple projection model of the magnetic field along the GPS signal path onto the horizontal plane when the signal paths were aligned no closer than 60° from the magnetic field. The shape of the scintillation fade pattern was greatly elongated in the magnetic north-south direction, and no change could be detected over a distance of 1 km. The east-west widths of the scintillation fade patterns were variable, but after normalizing to the elevation angle, accounting for the fade orientation, and eliminating signal paths within 60° of the magnetic field, an organized scale length of about 450 m was determined. The duration of the scintillation fade patterns was examined using the optimal cross-correlation amplitude as a measure of change. For a 5 s duration, 49% of the optimal cross-correlation amplitudes exceed a value of 0.8.

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