Wikipedia has this to say about solar particle events:

> A solar particle event (SPE), or "proton storm," occurs when particles
> (mostly protons) emitted by the Sun become accelerated to very high
> energies either close to the Sun during a solar flare or in
> interplanetary space by the shocks associated with coronal mass
> ejections.

Okay, so they seem to have to do with both solar flares and CMEs. And this page on part of the Goddard Space Flight Center website says:

> The super-heated electrons from CMEs move along the magnetic field
> lines faster than the solar wind can flow. Rearrangement of the
> magnetic field, and solar flares may result in the formation of a
> shock that accelerates particles ahead of the CME loop.

So is that what a proton storm is, a piece of a coronal mass ejection that was accelerated beyond the rest of the CME by interaction with a solar flare? How does that work?
 

  [1]: http://science.nasa.gov/science-news/science-at-nasa/2005/10jun_newstorm/