Generation of Assimilated Indian Regional Vertical TEC Maps

Abstract

Regional ionospheric total electron content maps have become a prominent tool for understanding the dynamic behavior of the ionosphere. In recent times, ionospheric data assimilation methods have enhanced the prediction capabilities of global ionospheric models by embedding several standalone ionospheric remote sensing observations. In this study, an attempt is made to generate hourly Assimilated Indian Regional Vertical Total Electron Content (AIRAVAT) Maps by the process of data assimilation using the Kalman filter exclusively for the Indian region (longitude: 65° to 100°; latitude: 5° to 40°). Observations from the ground-based Global Positioning System aided Geo-Stationary Orbit Augmented Network and radio occultations from the space-based Constellation Observing System for Meteorology, Ionosphere, and Climate are introduced into the global ionospheric map developed by the Centre for Orbit Determination in Europe with a temporal resolution of 1 h. The AIRAVAT maps are created for a day of quiet (September 16, 2016) and disturbed (October 25, 2016) geomagnetic conditions. A new methodology is provided for the covariance matrix of initial background model errors through multivariate principal component analysis of solar and geomagnetic parameters. The equatorial ionization anomaly features are clearly captured in the developed AIRAVAT maps by using both the updated and forecasted steps of the Kalman filter. The AIRAVAT model is validated with an independent GNSS receiver through root-mean-square error analysis for both quiet and disturbed geomagnetic conditions to showcase the efficiency of the model. The quiet day RMSEs between the estimated TEC of proposed AIRAVAT model and the true data are approximately 2 TECU and 2.66 TECU for a disturbed day, respectively. The proposed AIRAVAT maps are useful for monitoring the impact of ionospheric space weather on satellite-based navigation and communication systems.