3 He-rich Solar Energetic Particles from Sunspot Jets

Abstract

Solar sources of suprathermal (<1 MeV nucleon −1 ) 3 He-rich solar energetic particles (SEPs) have been commonly associated with jets originating in small, compact active regions at the periphery of near-equatorial coronal holes. Sources of relatively rare, high-energy (>10 MeV nucleon −1 ) 3 He-rich SEPs remain unexplored. Here we present two of the most intense 3 He-rich ( 3 He/ 4 He > 1) SEP events of the current solar cycle 24 measured on the Advanced Composition Explorer at energy >10 MeV nucleon −1 . Although 3 He shows high intensities, Z  > 2 ions are below the detection threshold. The events are accompanied by type-III radio bursts, but no type-II emission as typically seen for suprathermal 3 He-rich SEPs. The corresponding solar sources were analyzed using high-resolution, extreme-ultraviolet imaging and photospheric magnetic field observations on the Solar Dynamics Observatory . We find the sources of these events associated with jets originating at the boundary of large sunspots with complex βγδ magnetic configuration. Thus, details of the underlying photospheric field apparently are important to produce 3 He to high energies in the examined events.