  Discovered more than 40 years ago, impulsive solar energetic particle (SEP)
events are still poorly understood. The enormous abundance enhancement of the
rare 3He isotope is the most striking feature of these events, though large
enhancements in heavy and ultra-heavy nuclei are also observed. Recurrent
3He-rich SEPs in impulsive events have only been observed for limited time
periods, up to a few days which is typically the time that a single stationary
spacecraft is magnetically connected to the source active regions on the Sun.
With the launch of the two STEREO spacecraft we now have the possibility of
longer connection time to solar active regions. We examined the evolution of
source regions showing repeated 3He-rich SEP emissions for relatively long time
periods. We found that recurrent 3He-rich SEPs in these long-lived sources
occur after the emergence of magnetic flux.

Solar and Stellar Astrophysics