On the timescale and location of He-3 acceleration

George Simnett

Research output: Contribution to journalArticle


We present a novel explanation for the He-3-rich solar energetic particle events. We suggest that at low latitudes the coronal magnetic field is largely closed out to several solar radii. Quasi-continuous magnetic reconnection provides conditions suitable for resonant acceleration of He-3 which essentially accelerates all the ambient ions up to energies around 1 MeV/nucleon, which are largely trapped in the closed field. Electrons are also accelerated together with a relatively small number of ions which also satisfy the resonance condition. Ultra-heavy ions may also be accelerated, although details of how this is achieved are not known at this time. Reconnection in the outer region of the closed magnetic field injects the trapped particles from time to time into the interplanetary medium as impulsive events, while leakage provides a dribble of ions into the interplanetary medium, to provide the quiet time background. The trapped ions may also be seed particles for acceleration in a chromospheric flare. The flare acceleration does not preferentially accelerate He-3 nor ultra-heavy ions.
Original languageEnglish
Pages (from-to)469-480
Number of pages12
JournalAstronomy and Astrophysics
Issue number1
Publication statusPublished - 1 Nov 2009


  • Sun: corona
  • Sun: coronal mass ejections (CMEs)
  • Sun: particle emission


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