Particle acceleration and sources in the November 1997 solar energetic particle events

We report studies of two large solar energetic particle (SEP) events on Nov. 4 and 6, 1997 that were observed using advanced energetic particle detectors on the ACE and the Wind spacecraft. Both events showed enriched Fe/O, and had a ∼1 MeV/n ³He/4He ratio = 2.1 × 10−3, 4 times the coronal value. The Nov. 6 event had exceptionally hard spectra, with much higher intensities of high energy (10s of MeV) particles than the Nov. 4 event, yet below 1 MeV/n the intensities in the Nov. 6 event were lower than for Nov. 4. Strong, complex temporal variations observed for ∼120 keV Fe/O contrasted with only gradual changes of this ratio at ∼25 MeV/n. A spectral break was observed in the Nov. 6 event, wherein below a few MeV/n the spectra became harder. Taken together, these observations point to different seed and acceleration mechanisms dominating at low and high energies in these events.