Solar Source Regions for3He‐rich Solar Energetic Particle Events Identified Using Imaging Radio, Optical, and Energetic Particle Observations

Abstract

We have identified the sources of six impulsive 3He-rich solar energetic particle events using imaging radio, optical, and energetic ion and electron data, together with calculated coronal fields obtained from extrapolating photospheric magnetograms using a potential field source surface (PFSS) model. These events were all studied in 2006 by Wang et al., who identified the particle sources as typically small, flaring active regions lying next to a coronal hole containing Earth-directed open field lines, located between W33° and W65°. By introducing radio imaging data we were able in one case to conclusively identify which of two simultaneous EUV jets was associated with the particle source. In addition, type III radio burst and energetic electron data introduced in this study constrain the injection times much more accurately than possible with low-energy ion data used in Wang et al. These new observations confirm the source identifications of Wang et al. and remove many of the remaining uncertainties. All of these events were associated with narrow, fast coronal mass ejections (CMEs), which are unusual for 3He-rich solar energetic particle (SEP) events. Although the CMEs generally were ejected in directions well off the ecliptic plane, the PFSS calculations show the presence of magnetic field lines that made it possible for the energetic particle to quickly reach Earth. Some of these impulsive events were observed during periods in which 3He was observed continuously over several days.