Solar and latitude dependence of TEC and SLAB thickness

Several years of the vertical total electron content (TEC) and of the equivalent slab thickness data measured at different European locations are analysed by using the linear regression technique to demonstrate the annual response of these two ionospheric parameters to changes in solar activity and to their dependence on latitude. It is shown that TEC is highly correlated with the latitude and solar activity, whereas the slab thickness is independent of both solar activity and latitude. Their intercepts relative to solar activity show clearly a seasonal dependence.