A study of solar energetic particle events of 1997-2006: Their composition and associations

We examined the properties and associations of 280 solar proton events that extended above 25 MeV and occurred in the years 1997-2006. The properties include early peak intensities of five species over several energy ranges and the intensity-time profiles. Solar event associations were made for as many events as possible. The solar parameters determined include coronal mass ejection and flare properties and radio emissions from a wavelength range of meters to kilometers. The events were divided into five representative types based on the relative abundances and particle profiles to more easily illustrate how particle characteristics vary with the solar parameters. We find a continuum of event properties with no indication of specific parameters that clearly separate out groups of events. There is, however, a reasonable separation of events based on the timing of the associated type III emissions relative to the H a flare. Type III bursts indicate the presence of flare particles that escape to the interplanetary medium. The least intense, relatively short-lived, proton events that are electron-rich (and generally Fe-rich and He-rich) have associated type III bursts that occur at the start of the flare (i.e., in the impulsive phase), indicating rapid acceleration and escape of particles. In the largest events the type III emissions occur after the impulsive phase. It is likely that this late acceleration and/or release of particles results in a composition different from that of impulsive acceleration and release. A scenario in which concomitant flare processes contribute particles in the majority of solar energetic particle events is consistent with the observations.