Coronal Holes, Jets, and the Origin of3He‐rich Particle Events

Abstract

Using magnetograph measurements, coronal field extrapolations, and imaging observations, we investigate the solar origins of 25 3He-rich particle events from the period 1997-2003. In essentially every case we find that the source of the impulsive solar energetic particles (SEPs) lies next to a coronal hole containing Earth-directed open field lines. Averaged over all events, the source-hole separation is only ~4° at the photosphere. The source itself is typically a small, flaring active region located between longitudes ~W25 and ~W72. Around the estimated particle injection time, EUV images often show a jetlike ejection aligned with the open field lines. In some cases, a corresponding white-light jet is seen at heliocentric distances 2 R☉, similar to those studied earlier by Wang & Sheeley. The jets show a tendency to recur, a behavior that is reflected in the time variation of the measured 3He and Fe particle intensities. We interpret the jets as signatures of magnetic reconnection (footpoint exchange) between closed and open field lines. On the basis of these findings, we expect 3He enrichments to be observed whenever Earth-connected open field lines undergo footpoint exchanges with nearby active or ephemeral region fields. Because small bipoles emerge continually inside coronal holes, moderate enhancements in the 3He level can occur even when no significant flaring activity is recorded.