The performance of ionospheric correction based on NeQuick 2 model adaptation to Global Ionospheric Maps

Abstract

In this paper, the Global Ionospheric Maps (GIMs) during 1998–2012 have been adopted as the primary source of data to generate the Galileo-like ionospheric correction parameters. Taking the previous day GIMs as ingested dataset and the current day GIMs as reference, we have computed the cumulative distribution function (CDF) of TEC (Total Electron Content) error less than 5 TECU (TEC Unit, 1TECU=1016electron/m2) or 20% (denoted as zi20) to study the performance of NeQuick 2 in providing global ionospheric correction. The statistical analysis is carried out to study how the performance changes with seasons, solar activities and geographic latitudes. Our studies showed that: (1) in general, the NeQuick 2 model driven by the previous day GIMs agrees well with the current day GIMs, with monthly averaged zi20 exceeds 60%. (2) The performance of GIMs-driven-NeQuick model varies with geographic latitudes. The model behaves better in mid-latitudes than in low-latitudes, which is more prominent in northern hemisphere. (3) There is a nonlinear relationship between zi20 and F10.7. When the solar activity level is low or medium, zi20 tends to decrease with increasing solar activities. However, when F10.7 increases further to exceed a certain threshold, zi20 generally shows either saturation or an increase for high solar epoch. The zi20 decreases with F10.7 more sharply in mid-latitudes than in low-latitudes, in the southern hemisphere than in the northern hemisphere. (4) The seasonal behavior of zi20 in different latitudinal belts are quite different. In the southern hemisphere, zi20 mainly presents annual variation, and it is largest in winter and smallest in summer. In the northern hemisphere, the semi-annual variation is dominant, and zi20 is larger in solstice than in equinox. During the High Solar Activity years, the zi20 is much larger in summer than in winter in the low-latitude regions.