Midlatitude nighttime enhancement in F region electron density from global COSMIC measurements under solar minimum winter condition

Ionospheric electron density profiles retrieved from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites measurements from 6 November 2006 to 5 February 2007 are used to study the ionospheric nighttime electron density enhancements under winter, solar minimum, and geomagnetically quiet conditions. In this work, the peak electron densities of F₂ layer (N m F₂) derived from COSMIC measurements are found to be in reasonably good agreement with ionosonde observations during the night.

Therefore the morphology of nighttime enhancements is investigated at geomagnetic midlatitudes (MLAT 20 - 60°) in the northern hemisphere using COSMIC observations. The enhancements of electron density are evident near the F ₂ layer peak at most latitudes and longitudes; however, significant variations in the latitudinal dependence of the occurrence time and net magnitudes of the enhancements are found in different regions.