On the Development of a Method for Updating an Empirical Climatological Ionospheric Model by Means of Assimilated vTEC Measurements From a GNSS Receiver Network

In this paper, a procedure for updating the International Reference Ionosphere (IRI) model by
means of assimilated vertical total electron content (vTEC) measurements from a Global Navigational
Satellite Systems (GNSS) receiver network is presented. This procedure stands as an additional
implementation of the IRI UPdate (IRI UP) method, which is based on the assimilation of ionosonde derived
F2 layer ionospheric characteristics. According to this, a mathematical procedure for obtaining foF2 and
M(3000)F2 values from vTEC measurements is here proposed. Mathematical relationships between F2 layer
characteristics and vTEC values have been derived using South African colocated ionosonde and GNSS
stations. The same procedure can, however, be applied successfully in each region where such data are
available. The goodness of the proposed IRI UP method, based on assimilated vTEC values, has been tested
for several quiet and disturbed days in 2017 and 2018. IRI UP exhibits better performances than IRI for foF2,
for most of the analyzed cases. Slight improvements are achieved in modeling hmF2 only for very
disturbed periods in 2017. Due to the very good coverage of the terrestrial surface that GNSS receivers have
achieved in recent years, we suggest that the method proposed here can be a good implementation of the IRI
model for Space Weather nowcasting purposes, at least for foF2.