Abstract
In this paper, ground based Global Positioning System (GPS) Total Electron Content (TEC) observations collected from the GPS Aided GEO Augmented Navigation (GAGAN) network over low latitude Indian subcontinent are assimilated into the Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM). Gauss-Markov Kalman filter methodology is utilized and the background model error covariance (BMEC) matrix is framed using solar, geomagnetic, cross tail potential and hemispheric power indices using multivariate principal component analysis (MPCA) method. The model variations through different high latitude electric field models (Weimer and Heelis) are utilized in the data assimilation analysis. The proper attempt is modeled for providing TEC forecasts during geomagnetic storm conditions from 15th to 20th March 2015 days over Indian region. The more concentration is given in understanding the equatorial ionization anomaly (EIA) characteristics during the initial, main and recovery phase of St. Patrick’s Day March 2015 geomagnetic storm. The proposed model forecast outperforms the persistence forecast with maximum forecast score (1.6) and forecast skill (2.2) during recovery phase of storm. TEC forecasts are validated with current time step GPS observations and 93 % correlation is observed on quiet day (10th March 2015) and 82 % correlation is noticed on main phase of storm (17th March 2015). Also proposed TEC model analysis and forecast results are compared with International Global Navigation Satellite Service (IGS) TEC stations datasets. A clear negative storm effect (EIA inhibition) has been forecasted well with the proposed Kalman filter and MPCA methodology aspects.
Highlights
Equatorial ionization anomaly (EIA) is one of the major characteristic features observed over low latitudes that clearly signifies the storm time ionospheric variability [1]
Several magnetic field perturbations are recorded in Interplanetary Magnetic Field (IMF) Bz during geomagnetic storm conditions (Fig. 1(c))
No large RMSE deviations between model forecast and analysis are noticed by choosing Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM)/WEIMER and TIEGCM/HEELIS models
Summary
Equatorial ionization anomaly (EIA) is one of the major characteristic features observed over low latitudes that clearly signifies the storm time ionospheric variability [1]. The equatorial plasma fountain undergoes either enhancement or inhibition of electron density due to disturbance electric fields prevails during geomagnetic storm conditions [1], [2]. The integrated electron density is termed as Total electron content (TEC) is a key parameter for investigating ionospheric variability occurred during positive/negative geomagnetic storm. The ionospheric perturbations and forcing parameters should be considered to model TEC observations during geomagnetic storm conditions [3]. EIA expands to wider latitudes at the time of geomagnetic storm, compared with the plasma fountain driven by E and F layer dynamo electric fields during quiet ionospheric condition over low latitude region [4], [5]. The influence during main and recovery phase of storm for equatorial, low latitude region is clearly visualized from EIA crest regions during geomagnetic storm conditions [6]
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