The Level-2 Electron Density Profiles data product contains F-region electron density as a function of altitude and latitude derived from the GUVI limb data. Summaries of estimated peak electron density and total electron content are also given as Level 3 products. The profiles are derived from the 135.6-nm channel of the GUVI limb data. The 135.6-nm emission at night is due almost exclusively to recombination of O+ ions. Since O+ is the primary ion in the F region, the 135.6-nm volume emission rate is closely related to the square of the electron density. Details of the procedure of producing the electron densities are given in: DeMajistre, R., L.J. Paxton, D. Morrison, J-H. Yee, L.P. Goncherenko and A.B. Christensen, Retrievals of nighttime electron density from Thermosphere Ionosphere Mesosphere and Dynamics (TIMED) mission Global Ultraviolet Imager (GUVI) Measurements, J. Geophys Res., 109, A05305, doi:10.1029/2003JA010296.