Suprathermal Particle Measurements with Solar Orbiter

Solar Orbiter, a joint ESA/NASA mission, is designed to study the Sun and inner heliosphere in greater detail than ever before. At the closest point on its heliocentric orbit, the Solar Orbiter spacecraft will be about 0.3 AU from the Sun. Understanding the physical processes operating in Solar Energetic Particle (SEP) events is a major goal of the Solar Orbiter mission because of the importance of acceleration processes in solar system and astrophysical sites, and because of the potential impact of these events on space hardware and on human activities in space in general. The Energetic Particle Detector (EPD) investigation on Solar Orbiter is a suite of four different sensors plus the instrument control unit to measure the energetic particles from slightly above solar wind energies to hundreds of MeV/nucleon. During the first two years in orbit, SIS observed multiple gradual and impulsive SEP events inside of 1 au. We observe variations in the suprathermal ions from these impulsive SEP that are enriched in ³He. We make comparison of these variations with various solar activities and determine the fraction of time the inner heliosphere is filled with these ³He. We compare these new observations with properties similar to those previously observed at 1 au, promising new insights as Solar Orbiter moves much closer to the Sun in 2022.