MPS Seminar: Advances in understanding of 3He-rich solar energetic particles with solar source observations (Radoslav Bucik)

3He-rich solar energetic particle (SEPs), showing up to a 10,000-fold abundance enhancement of rare elements like 3He or ultra-heavy nuclei, have been a puzzle for more than 50 years. One reason for the current lack of understanding of 3He-rich SEPs is the difficulty resolving the source regions of these commonly occurring events. Since their discovery, there has been strong evidence that 3He-rich SEP production is associated with flares on the Sun. Anomalous abundances of 3He-rich SEPs have been attributed to a unique acceleration mechanism that must routinely operate at flare sites. Flares associated with 3He-rich SEPs have been often observed in jet-like forms indicating an acceleration in magnetic reconnection involving field lines open to interplanetary space. Owing to a fleet of spacecraft around the Sun, providing a greatly improved resolution of solar imaging observations, 3He-rich SEP sources are now explored in unprecedented details. As an example, helical jets with unwinding motion have been observed in events with extreme 3He and heavy-ion enrichment, or wide-spread 3He-rich SEP events were found to be accompanied by large-scale propagating coronal waves. Implications for ion acceleration and injection into interplanetary space arising from imaging observations of 3He-rich SEP solar sources will be discussed.