Energetic Particle Fluxes during the Bastille Day Solar Eruption

Abstract

We report on our observations of solar energetic particle fluxes of p, He, C, O, Ne, Mg, Si, and Fe ions measured by the Energetic and Relativistic Nucleon and Electron (ERNE) experiment associated with the Bastille Day solar flare and coronal mass ejection (CME) on 14 July 2000. We observed two clear maxima of the Fe/O ratio at the energies 8.5–15 MeV nucl−1. The first Fe/O maximum occurred ∼ 3 hours after the beginning of the particle event, and the second maximum ∼ 22 hours after the first one at the arrival of the shock associated with the Bastille Day eruption. We also observed a change in the energy spectrum of oxygen concurrent with a change in the direction of the interplanetary magnetic field at the start of the second enhancement of the Fe/O ratio. We propose an interpretation of the particle event where observed interplanetary particle fluxes are associated with two different particle sources near the Sun and in interplanetary space. We suggest that heavy ions observed during the first period of the Fe/O enhancement were released when a coronal shock reached a magnetic foot point connected to 1 AU. The second maximum of Fe/O occurred when spacecraft encountered Fe-rich material stored in magnetic field flux tubes early in the event and was possibly reaccelerated by the interplanetary shock.