SOHO/energetic and relativistic nucleon and electron experiment measurements of energetic H, He, O, and Fe fluxes during the 1997 November 6 solar event

A brilliant solar X-ray and Ha flare and a coronal mass ejection (CME) on 1 997 November 6 were associated with high particle fluxes in interplanetary space at energies above MeV. The CME had an exceptionally high leading edge velocity (1560 km s(-1)) as observed by the Large Angle and Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observatory (SOHO). The Energetic and Relativistic Nucleon and Electron experiment (ERNE), als o on SOHO, measured high H, He, O, and Fe fluxes in several energy channels from 3 to 200 MeV nucleon(-1). The oxygen energy spectrum in energy range 3-200 MeV nucleon(-1) was of a broken-power-law form with a break around 50 MeV nucleon(-1). In addition, ERNE observed abrupt changes in the intensit y, elemental composition, and anisotropy of high-energy particles, which ma y indicate two energetic particle sources during several hours after the so lar flare eruption. The observational results lead us to conclude that, mos t of the time, the O and Fe nuclei were injected by the interplanetary shoc k associated with the coronal mass ejection emitted around 12 UT on Novembe r 6. However, during two time periods the injection source might have been different or complementary. The first period was in the very beginning of t he event, 13:20-13:40 UT, when the particle streaming showed very strong an isotropy with the maximum intensity from the direction of the Sun. The seco nd was between 17 UT November 6 and 5 UT November 7, when particle fluxes w ere dominated by a particle population with a different elemental compositi on and a different spectral shape of O as compared with the particle popula tion prevailing in the beginning and during the long decay phase of the eve nt. We propose that the source of these particles was associated with a cor onal shock wave traveling in the low solar atmosphere.