A Novel Technique to Determine Ionic Charge States in Large Solar Particle Events

We present a novel technique to measure average ionic charge states of high energy (/geq 10 MeV/nuc) solar energetic particles (SEPs) in large solar events. It is found that in some large SEP events, the characteristic decay times of SEP fluxes decrease with increasing energy, in a manner consistent with a diffusion coefficient that increases with rigidity. From this dependence average ionic charge states are inferred for nitrogen, oxygen, neon, magnesium, silicon, sulfur, and iron in several SEP events between 1997 and 2002. There is considerable variation in the charge state of iron from event to event. For those SEP events for which charge states have been determined with SAMPEX/MAST using the geomagnetic cutoff technique, the results from both techniques are seen to be consistent.