High Energy Ionic Charge State Composition In Recent Large Solar Energetic Particle Events

The ionic charge states of solar energetic particles (SEPs) provide information on the temperature of source materials and on conditions during acceleration and transport. SAMPEX/MAST measures mean ionic charge states at > 15 MeV/nuc using the geomagnetic rigidity filter technique. Charge state measurements by MAST for gradual SEP events suggest a continuum of charge states correlated with abundance ratios for a variety of elements, similar to what is observed at lower energies. In cases where lower energy measurements are also available, the combined measurements indicate energy dependent charge states. We have completed ionic charge state measurements for 17 SEP events from solar cycle 23. We discuss the implications of our results.