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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?

I used to think that SPEs were CMEs hitting Earth, but that doesn't seem to be the case, or at least only sometimes. After all, why have two terms if they are the same thing? I'm especially interested in it because of the highly variable time it takes for an SPE to reach the Earth. Under the right conditions, they move almost at the speed of light - there was one like that documented in 2005. So the way storms develop, and how that affects their speed, makes a big difference to how people and spacecraft need to be protected against them.

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  • $\begingroup$ Do you think the good people at Astronomy SE may know the answer to this? $\endgroup$ – Rikki-Tikki-Tavi Jul 5 '15 at 11:02
  • $\begingroup$ @Rikki-Tikki-Tavi I went and checked and haven't found anything. I could have asked there, but it is an area that overlaps with Space Exploration SE, and since this is really where i spend my time, i asked here. (At some point i'd like to spend time there too, but not right now. I can't spare any more time.) $\endgroup$ – kim holder Jul 5 '15 at 14:33
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    $\begingroup$ Terminology is a bit fuzzy here. To my understanding, SPE is but a measured effect of proton flux at different energy levels, but it can be caused by a number of things. So if a flare causes an acceleration of charged ions in CME or solar wind, it will create a bow shock moving at greater speed than the rest of the particle density that was unaffected by flare's charge or even decelerated. That then causes detection of a whole range of different eV level particles, first the flare itself at the highest order, then the bow shock of sped up CME's mass, and eventually the rest of the CME. $\endgroup$ – TildalWave Jul 5 '15 at 14:52
  • $\begingroup$ Can this be migrated to Astronomy? $\endgroup$ – Muze the good Troll. Apr 9 at 22:03

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