Ring Current Measurements
Top: plot showing the CIS/CODIF 27-39 keV proton channel (90° pitch-angle) during a traversal of the ring current on 20 April 2002. The connected squares are the values of the ion fluxes retrieved through an inversion algorithm from the simultaneously obtained data in the 27-39 keV hydrogen channel by the High-Energy Neutral Atom imager (HENA) instrument onboard the NASA spacecraft IMAGE. They represent what Cluster would measure if it flew through the inversion.
Lower left: ENA image in the 27-39 keV channel obtained by IMAGE/HENA.
Lower right: the 27-39 kev proton intensities in the equatorial plane retrieved by applying an inversion algorithm to the ENA image at lower left. The inversion algorithm assumes pitch-angle isotropy, Tsyganenko  magnetic field model, and the Ostgaard et al.  geocoronal model.