Fig. 4From: Ionospheric electron density modelling using B-splines and constraint optimizationF3C electron density profiles \(N_e = N_e({\varvec{x}}_{\mathrm {F3C}})\) (green) and GRACE electron density profiles \(N_e = N_e({\varvec{x}}_{\mathrm {GRACE}})\) (red) during the time interval 00:00 UT to 04:00 UT on March 12, 2015Back to article page