Abstract We have investigated the arrival times of species H–Fe in 3 He-rich solar energetic particle (SEP) events to determine if a common acceleration mechanism is responsible for all the ions, assuming that if the particles arrive simultaneously this is evidence of a common mechanism. Compared to other SEP populations, the extremely large enrichment of 3 He and much smaller though significant heavy ion enhancements suggest a common origin but without firm observational evidence due to the small size of the events. Using improved instruments close to the Sun on Solar Orbiter, we surveyed the period 2020 April—2025 May for 3 He-rich events whose rise phase phases were sufficiently undistorted and intense that the particle arrival times could be measured accurately. We found six events that met the criteria and that appear to be typical impulsive SEP events but with unusually high counting statistics. For C–Fe the mean arrival times of 226–320 keV nucleon −1 ions are simultaneous to ∼5 minutes, a small fraction of the ion propagation time from the Sun (110–310 minutes depending on heliocentric distance). H and 4 He mean arrival times showed a maximum difference of 1.6 minutes. Overall 3 He arrival times differ from the others by ∼3 ± 3 minutes. These times are sufficiently close to simultaneity to give evidence for a common acceleration mechanism. This adds a new constraint to models for these events, namely, that the accelerating waves can interact with the broad range of gyrofrequencies associated with the range charge-to-mass ratios for H–Fe.
Mason et al. (Wed,) studied this question.