Seed Population for 3He Enhancements in Large Solar Energetic Particle Events
G. M. Mason, J. E. Mazur, J. R. Dwyer
	University of Maryland, College Park, Maryland USA

We have measured the 3He abundance from ~0.5-2 MeV/nuc in 12 large solar energetic particle (SEP) events during the period November 1997 - June 1999. In 5 of the events, the 3He time-intensity profile is similar to the 4He time-intensity profile, indicating a common acceleration and transport origin for the two species. The average 3He/4He ratio during these events is 1.9 0.2 x 10-3, a factor of ~5 enhancement over the solar wind value. During this same survey period we have also measured the low energy ion intensities during quieter periods in-between the large particle events. We find 3He and Fe remnant from impulsive events present on a majority of the days, implying that they fill a substantial volume (>50%) of the in-ecliptic interplanetary medium during our survey. We suggest that these suprathermal ions may therefore be a source population that is available for further acceleration by interplanetary shocks that accompany large SEP events, thereby leading to the 3He enhancements in a significant fraction of large SEP events. This impulsive SEP event material might also account for recent observations of large solar particle events with energetic particle ionization states that have a wide range of ionization states that encompass values expected for both gradual and impulsive solar SEP events.