ROLE OF CURRENT SHEETS IN THE MODULATION OF SOLAR ENERGETIC PARTICLE EVENTS

Recent results have clarified the way in which solar energetic (E > 10 MeV) particles (SEPs) are produced in the solar corona and interplane tary medium. The principal result is that most SEPs in large events ar e accelerated on open field Lines by large-scale shocks driven by coro nal mass ejections (CMEs). However, the large range of timescales for different SEP events associated with solar source regions at comparabl e longitudes suggests that the shocks are somehow strongly modulated n ear the Sun. We investigate the possibility that the coronal streamer belt and current sheet provides a barrier for shock propagation and as sociated SEP acceleration, as suggested in several recent studies. We use solar flares as proxies for CMEs and plot on the Stanford source s urface maps the positions of flares associated with large (F > 10 p/cm (2)sr s at E > 10 MeV) SEP events observed at the Earth. The basic que stion is whether SEPs are preferentially observed when the Earth occup ies the same magnetic sector as the associated solar flare. We find th at onset times, risetimes, and peak fluxes are essentially the same fo r SEP events with flares in the same sector as for those in the opposi te polarity sectors. This suggests that the streamer structure has no detectible effect on the development of the shock and CME driver. We d iscuss several alternative possibilities to explain the large variatio n in SEP event timescales.