On Geolocation Uncertainty in Radio Occultation Observations for Ionospheric Scintillation Monitoring at Alaska

Abstract

This paper presents an analysis of spatial-temporal relationships of ionospheric scintillation activities between COSMIC-1 radio occultation (RO) observations and a ground-based ionospheric scintillation monitoring (ISM) receiver in Alaska. The objective is to understand the ionosphere irregularity geolocation uncertainty in the RO observations. Two intense geomagnetic storms commenced on 20 and 31 December 2015 are used in this study. Three aspects of research are conducted. First, time lags between the RO scintillations and the ISM observations of the same irregularity events during the storms are characterized. Then, according to the time lags and ionospheric irregularity drift velocities inferred from the ground-based ISM receivers, the RO irregularity locations are adjusted. Finally, the new locations of the RO irregularity are compared with the RO signal tangent points to evaluate their geolocation uncertainty. Our results indicate the RO scintillation observations in the vicinity of the ground-based GNSS area are closely correlated with the scintillation indices generated by the ISM receivers within a time window ranging from a few minutes to 2.5 hours. The distance between the RO tangent points and the irregularity front inferred from ground observations suggests the uncertainty in the geolocation of the RO observations is in the range of several hundred to 7000 km (in both X and Y coordinates). Future study is needed to verify the results above.