Ionosphere F-region (IMAGE) Naval Research Laboratory Caption This is a contour plot of the electron density as a function of magnetic local time (MLT) and altitude. A fully 3-D spatial model of ESF describes the motion of ions along and transverse to the geomagnetic field in a narrow longitudinal wedge of the post-sunset ionosphere. Credit Naval Research Laboratory (2010) Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.