A Survey of Inferred Ionic Charge States for Solar Energetic Particle Events with Data from the ACE and STEREO Missions

At previous AGU Meetings and at the International Cosmic Ray Conference in Brazil in 2013, we demonstrated the method of Sollitt et al. (2008) for inferring high energy ionic charge states using sample SEP events from both the ACE and STEREO missions. In this method, intensity decay times during SEP events were fitted for each element for various energies, using data from the ACE/SIS instrument for the 6 Dec 2006 SEP event and the STEREO/LET Ahead instrument for the 27 Jan 2012 SEP event. Mean ionic charge states were then inferred from fits to these decay times. (Sollitt et al. (2008) also reported results using ACE/SIS data and ACE/ULEIS data for earlier SEP events.) While the earlier work applied the method to manually selected SEP events, we will report in this meeting results of applying the method to all large SEP events from the publicly available ACE/SIS and STEREO/LET data sets. This survey will be accomplished by applying the method to a scripted search through the complete data sets, although we expect only ~10% of the large SEP events to yield results, similar to the yield obtained by Sollitt et al. (2008). Through this search, we hope to obtain multi-spacecraft observations of inferred charge states that may reveal evidence of seed population variation with longitude or other evidence of longitude variation with charge state.