Seasonal Differences in the Dusk Equatorial Topside Ionosphere Measured by C/NOFS and DMSP

The C/NOFS spacecraft is in a near-equatorial elliptical orbit with an apogee of about 845 km which precesses through all local times over a period of about 66 days. The four operational DMSP spacecraft are in sun-synchronous circular polar orbits at roughly the same altitude as C/NOFS’s apogee. Thus the C/NOFS apogee overlaps with the DMSP duskside orbits every 66 days for a period of about two weeks. This work will present the analysis of three of these overlap periods during the northern winter (roughly December 30, 2008-January 12, 2009), the northern summer (roughly July 14-31, 2009), and one equinox period (roughly March 6-21, 2009) where we will use the combined C/NOFS and DMSP data to show the seasonal changes in ion density, composition, and temperature in the topside ionosphere. This will allow a further validation of the CINDI plasma instruments on C/NOFS as well as establishing a baseline of these geophysical parameters in the topside ionosphere through all seasons during the current extreme solar minimum conditions.