SOLAR PARTICLE EVENT WITH EXCEPTIONALLY HIGH ~3He ENHANCEMENT IN THE ENERGY RANGE UP TO 50 MeV NUCLEON~(-1)

摘要

We have surveyed the ~3He-rich solar particle events in the energy range of greater than 15 MeV nucleon~(-1) observed with the energetic particle instrument ERNE (the Energetic and Relativistic Nuclei and Electron experiment) on board the Solar and Heliospheric Observatory during 1999-2000. The survey reveals the exceptional event of 2000 October 29, with very strong ~3He enhancement persisting over the high-energy range, up to 50 MeV nucleon~(-1). This is the first time that the ~3He/~4He > 1 has been recorded at above 10 MeV nucleon~(-1). We present the first ever measurement of the ~3He energy spectrum in such an event. The particle event was associated with an impulsive flare and an interplanetary shock wave. The type II radio burst was observed with the WAVES experiment on board the Wind spacecraft before and then simultaneously with the ~3He-rich event registered with ERNE. The analysis shows that the high-energy ~3He-rich event refers to the flare material reaccelerated by the interplanetary coronal mass ejection (CME). Onset of the high-energy ~3He-rich event was observed in the far upstream region, when the CME-driven shock was at about 0.3 AU from the Sun. A spectrum of protons and spectra of the two helium isotopes closely resemble an exponent in the ion speed.