Role of current sheets in the modulation of solar energetic particle events

Authors:
  • SKS. W. Kahler
    S. W. Kahler
  • JKJ. M. Kunches
    J. M. Kunches
  • DSD. F. Smith
    D. F. Smith
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Abstract
Recent results have clarified the way in which solar energetic (E > 10 MeV) particles (SEPs) are produced in the solar corona and interplanetary medium. The principal result is that most SEPs in large events are accelerated on open field lines by large‐scale shocks driven by coronal mass ejections (CMEs). However, the large range of timescales for different SEP events associated with solar source regions at comparable longitudes suggests that the shocks are somehow strongly modulated near the Sun. We investigate the possibility that the coronal streamer belt and current sheet provides a barrier for shock propagation and associated SEP acceleration, as suggested in several recent studies. We use solar flares as proxies for CMEs and plot on the Stanford source surface maps the positions of flares associated with large (F > 10 p/cm2sr s at E > 10 MeV) SEP events observed at the Earth. The basic question is whether SEPs are preferentially observed when the Earth occupies the same magnetic sector as the associated solar flare. We find that onset times, risetimes, and peak fluxes are essentially the same for SEP events with flares in the same sector as for those in the opposite polarity sectors. This suggests that the streamer structure has no detectible effect on the development of the shock and CME driver. We discuss several alternative possibilities to explain the large variation in SEP event timescales.

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