Validation of GNSS-derived global ionosphere maps for different solar activity levels: case studies for years 2014 and 2018

Abstract Ionosphere Associate Analysis Centers (IAACs) of the International GNSS Service (IGS) independently produce global ionosphere maps (GIMs) total electron content (TEC). The GIMs are based on different modeling techniques, resulting in TEC levels and accuracies. In this study, we evaluated accuracy consistency IAAC during high (2014) low (2018) solar activity periods 24th cycle. our applied two evaluation methods. First, carried out a comparison GIM-derived slant (STEC) with carrier phase geometry-free combination signals obtained from 25 globally distributed stations. Second, vertical (VTEC) was compared to altimetry-derived VTEC Jason-2 Jason-3 satellites complemented for plasmaspheric TEC. analyzed STEC RMS values reaching 1.98 3.00 TECU 0.96 1.29 2014 2018, respectively. altimetry data resulted STD that varied 3.61 5.97 1.92 2.78 results show among IAACs, Center Orbit Determination Europe performed best periods. However, highest by non-IGS product—UQRG provided Universitat Politècnica de Catalunya. It also shown were using modified single layer model mapping function map time interval has relatively small influence accuracy.