A THREE-DIMENSIONAL APPROACH TO IMPROVE THE INTERNATIONAL REFERENCE IONOSPHERE (IRI) MODEL

Abstract. A three-dimensional model based on time and location is introduced to enhance the accuracy of vertical total electron content (VTEC) global ionosphere maps (GIMs) empirical models. The chosen International Reference Ionosphere 2016 (IRI-2016) observations are GIMs VTEC values from Center for Orbit Determination in Europe (CODE). For this purpose, IRI-2016 considered as a background VTECs correction term. term modelled using spherical harmonics expansion base functions with degree equal 15 Earth-fixed coordinate system polynomial B-spline function resolution. improved constructed 1st January 2018 Kp index 4. root mean square error (RMSE) improvements range 1.65 TECU 2.81TECU about 70 percent 85 bias 0.28 1.00 an average 0.75 TECU, respectively.