Comparative testing of four ionospheric models driven with GPS measurements

Abstract

In the context of the European Space Agency/European Space Operations Centre funded Study “GNSS Contribution to Next Generation Global Ionospheric Monitoring,” four ionospheric models based on GNSS data (the Electron Density Assimilative Model, EDAM; the Ionosphere Monitoring Facility, IONMON v2; the Tomographic Ionosphere model, TOMION; and the Neustrelitz TEC Models, NTCM) have been run using a controlled set of input data. Each model output has been tested against differential slant TEC (dSTEC) truth data for high (May 2002) and low (December 2006) sunspot periods. Three of the models (EDAM, TOMION, and NTCM) produce dSTEC standard deviation results that are broadly consistent with each other and with standard deviation spreads of ∼1 TECu for December 2006 and ∼1.5 TECu for May 2002. The lowest reported standard deviation across all models and all stations was 0.99 TECu (EDAM, TLSE station for December 2006 night). However, the model with the best overall dSTEC performance was TOMION which has the lowest standard deviation in 28 out of 52 test cases (13 stations, two test periods, day and night). This is probably related to the interpolation techniques used in TOMION exploiting the spatial stationarity of vertical TEC error decorrelation.

Modelling the main ionospheric trough using the Electron Density Assimilative Model (EDAM) with assimilated GPS TEC

“…Previous studies (e.g. Angling and Jackson-Booth, 2011;Feltens et al, 2011) have shown that EDAM can accurately represent the ionosphere using GNSS data.…”

Consistency of seven different GNSS global ionospheric mapping techniques during one solar cycle

“…Such directly observed dSTEC value is typically more accurate than 0.1 TECU (the measurement -thermal noise and multipath-error) and independent of any assumption or model (see more details in [6]). In this sense, dSTEC provides an excellent electron content reference in the (slant) transmitterreceiver line-of-sight, very useful to assess and compare the performance of different ionospheric models.…”

MONITOR Ionospheric Network: two case studies on scintillation and electron content variability

“…Several geoeffective solar flares occurred from days 70 to 76, 2015 (11 to 17 March), prior to the St. Patrick's Day storm, and these were detected and notified in real time by the MONITOR system by means of the GNSS solar flare indicator, (GSFLAI; Hernández-Pajares et al, 2012;MonteMoreno and Hernández-Pajares, 2014;Singh et al, 2015) and the sunlit ionosphere sudden TEC enhancement detector (SISTED; García-Rigo, 2012). Figures 18 and 19 show the corresponding plots for the days surrounding the St. Patrick's Day storm.…”

“…In order to evaluate the proposed ingestion-assimilation method, two different key indicators were considered: the differential slant GPS TEC (dSTEC; as defined for instance by Feltens et al, 2011) and slant GPS TEC calibrated with the UQRG GIMs (STEC). To perform this test, specific MONITOR products (externally provided or derived from internal processors) were used.…”