Regional ionospheric TEC data assimilation and forecasting during geomagnetic storm conditions for 17th and 18th March 2015 days

Ionospheric data assimilation method has been highly successful for forecasting spatial and temporal ionospheric variability. In this paper, an attempt is made to improve International Reference Ionosphere (IRI) model predictions over Indian region using Kalman filter approach of data assimilation. To image the ionospheric vertical total electron content (VTEC) over the entire Indian geographical region the TEC observations from Global Positioning System (GPS) receivers, GPS radio occultation ray paths and ionosonde datasets are utilized. The nonstationary background error covariance matrix and covariance localization are implemented including the solar and geomagnetic indices through multivariate principal component analysis (MPCA) method to obtain better ionospheric VTEC forecast. The proposed regional ionospheric VTEC model is named as Assimilated Indian Regional VerticAl TEC (AIRAVAT) model that generates forecast and analysis maps with 15 minutes of temporal resolution and 1° x 1° spatial resolution along 5° N to 40° N geographic latitudes and 65° E to 100° E geographic longitudes. The focus is to realize the variations in equatorial ionization anomaly (EIA) structures over the Indian region during geomagnetic storm conditions. AIRAVAT Model behavior during a major geomagnetic storm day of solar cycle 24 i.e., 17^th and 18^th March 2015 are presented. International Global Navigation Satellite System (GNSS) Service (IGS) stations at Hyderabad (HYDE), Lucknow (LCK4) and Lhasa (LHAZ) locations are considered as truth data for model validation.