Measurements of the Ionic Charge States of Solar Energetic Particles Using the Geomagnetic Field

The mean charge states of C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca, Fe, and Ni ions with ~15-70 MeV nucleon^(-1) in the two large solar energetic particle (SEP) events of 1992 October 30 and November 2 have been determined using measurements of the invariant latitude of the cosmic-ray cutoffs of these elements from the Mass Spectrometer Telescope on the polar-orbiting SAMPEX satellite. The deduced charge state values are in good agreement with the mean values measured directly in previous SEP events at much lower energies of ~1 MeV nucleon^(-1). The inferred equilibrium source temperatures are confirmed to be typically 2 × 10^6 K, which provides additional evidence that SEPs in gradual-type events are accelerated coronal material.