Abstract According to the evolutionary properties of the flare, halo coronal mass ejection (CME), enrichments of 3He ions in the energy range of 3.5–26 MeV nucl−1 and Ne, Mg, Si and Fe ions in the energy range of 8.5–15 MeV nucl−1, we argue that the 3He and heavy ions originate in the middle corona (~0.1–1 R⊙) with well-connected open field lines to the Earth, where the magnetic reconnection leads to acceleration of the electrons and the production of type-III burst during the decay phase of the soft X-ray emission. The acceleration of 3He and heavy ions may have been accomplished in two stages: first H-He ion-ion hybrid waves may be easily excited by the energetic electron beams produced in the middle corona, and these waves are preferentially absorbed by 3He and heavy ions due to their frequency being near the fundamental gyro frequency of the 3He ions and harmonic gyro frequency of Ne, Mg, Si and Fe ions. These preheated ions escape into interplanetary space along the open field lines and may be further accelerated to tens of MeV nucl−1 by CME-driven shock. The theoretical calculations show that the 3He and heavy ions may be accelerated to the energy of ~ MeV nucl−1 by the ion-ion hybrid waves and be further accelerated to the energy of ~ 100 MeV nucl−1 by the shock wave: these are basically consistent with the observations.
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