We use the quite time F region  equatorial vertical drift model by Scherliess and Fejer (1999) for the climatological part of the real time calculator. The Scherliess and Fejer (1999) model describes the diurnal and seasonal variations in the ionospheric vertical drift for all longitudes and for all solar flux conditions.  The model was derived from the incoherent scatter radar observations at Jicamarca and Ion Drift Meter observations by the Atmospheric Explorer E satellite. The vertical drift is converted to the equatorial ionospheric east ward electric field by multiplying it with the magnetic field strength along the dip equator determined from the CHAMP data (Luhr et al., 2004).

Reference:

• Scherliess, L. and Fejer, B.G. (1999). Radar and satellite global equatorial F region vertical drift model. Journal of Geophysical Research 104(A4): doi: 10.1029/1999JA900025.
• Luhr, H., S. Maus, and M. Rother (2004), Noon-time equatorial electrojet: Its spatial features as determined by the CHAMP satellite. Journal of Geophysical Research 109 A01306: doi: 10.1029/2002JA009656.