Validation of Ionospheric Spatial Decorrelation Observed During Equatorial Plasma Bubble Events

A postprocessing methodology is developed to validate abnormal ionospheric spatial decorrelation observed during the equatorial plasma bubble (EPB) events. While the Global Navigation Satellite System (GNSS) remote sensing techniques have been used to measure the ionospheric gradients, the measurements can be easily corrupted during the ionospheric disturbances. Extremely large ionospheric gradients are required to be validated before being declared real ionospheric events as opposed to the artifacts of erroneous measurements. The use of existing methods is however limited due to the small size of EPBs compared with the baseline distances between GNSS network stations in equatorial regions. This paper proposes a new validation procedure which utilizes a time-step method to estimate gradients over any short distance. Equatorial anomaly events are visualized in multiple time series by combining all available sources, including severe gradients observed from the multiple widely spread stations, the estimated EPB and known satellite motions, and the known station locations. A similar ionospheric pattern over multiple station-satellite pairs supports the fact that they are impacted by the same EPB at different times and locations. An extreme ionospheric gradient of 3.09 TECU/km observed in the Brazilian region during the December 31, 2013 EPB event is validated to be real using this methodology. The results demonstrate the effectiveness of the methodology for validating EPB-induced ionospheric spatial decorrelation.