Characteristics of 3He-rich Solar Energetic Particle Events Derived from in situ Observations

Extensive in situ observations of 3He-rich solar energetic particle (SEP) events were made during cycle 23 using instruments on a variety of spacecraft including ACE, Wind, and SoHO. The combined data set, which has essentially no data gaps over a period of >10 years, has proven useful for both statistical and case studies of these events. The modern instrumentation flown on these spacecraft made it possible to measure: spectra over a broad energy range, abundances of rare elements and of element groups in the upper 2/3 of the periodic table, isotopic composition of several heavy elements, and timing and three-dimensional anisotropy distributions of arriving particles. The advances that have been made in our understanding of 3He-rich SEP event characteristics as the result of these observations will be discussed. In addition, the expected contributions from the STEREO mission, which was launched in late 2006, will be mentioned. This work was supported by NASA under grants NAS5-12929 and NAS5-03131.