Helium ion Measurements From the Arecibo Incoherent Scatter Radar and the DMSP Satelites

Data from the Arecibo incoherent scatter radar (ISR) and the DMSP-F13 (Defense Meteorological Satellite Program) satellite are presented and compared. Observations from periods exhibiting the He+ layering phenomenon are analyzed. Historically, there has been little attempt to compare data from the two sources due to difficulties in combining ground-based and space-based studies; also, only recently have light ion concentration measurements from Arecibo been possible in the topside ionosphere up to 2000 km altitude. The results presented show favorable comparison between the two data sources, giving users increased levels of confidence in the observations. Regions where the helium ions are of comparable concentration to the major ions (O+ and H+) are apparent in the data, serving to reinforce the view that the helium ion should not be regarded as a minor ion under all conditions.