Beschreibung:
<jats:title>Abstract</jats:title>
<jats:p>Particle acceleration in stellar flares is ubiquitous in the universe; however, our Sun is the only astrophysical object where energetic particles and their source flares can both be observed. The acceleration mechanism in solar flares, tremendously enhancing (up to a factor of 10,000) rare elements like <jats:sup>3</jats:sup>He and ultra-heavy nuclei, has been puzzling for almost 50 years. Here we present some of the most intense <jats:sup>3</jats:sup>He- and Fe-rich solar energetic particle events ever reported. The events were accompanied by nonrelativistic electron events and type-III radio bursts. The corresponding high-resolution, extreme-ultraviolet imaging observations have revealed for the first time a helical structure in the source flare with a jet-like shape. The helical jets originated in relatively small, compact active regions, located at the coronal-hole boundary. A mini-filament at the base of the jet appears to trigger these events. The events were observed with the two <jats:italic>Solar Terrestrial Relations Observatories</jats:italic> on the backside of the Sun, during the period of increased solar activity in 2014. The helical jets may be a distinct feature of these intense events that is related to the production of high <jats:sup>3</jats:sup>He and Fe enrichments.</jats:p>