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

Creators: Mason, G. M.; Cohen, C. M. S.; Cummings, A. C.; Dwyer, J. R.; Gold, R. E.; Krimigis, S. M.; Leske, R. A.; Mazur, J. E.; Mewaldt, R. A.; Möbius, E.; Popecki, M.; Stone, E. C.; von Rosenvinge, T. T.; Wiedenbeck, M. E.

Abstract

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.

Additional Information

© 1999 by the American Geophysical Union. Received September 4, 1998; revised November 2, 1998; accepted November 11, 1998. Paper number 1998GL900235. We thank the many individuals at the University of Maryland, Caltech, Jet Propulsion Laboratory, NASA Goddard Space Flight Center, Johns Hopkins Univ. APL, and University of New Hampshire for the construction of the instruments. We thank C. Smith and D. McComas and the ACE MAG and SWEPAM teams for the shock identifications used here; R. Lepping and the Wind MFI team for the magnetic cloud identification; K. Ogilvie and the Wind SWE team for the solar wind speeds. This work was supported in part by NASA grants NAG 5-7228, NAG5-6912 and PC 251428.

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