Solar energetic particles

They consist of protons, electrons and heavy ions with energies ranging from a few tens of keV to many GeV.

These can originate either from a solar flare site or by shock waves associated with coronal mass ejections (CMEs).

SEPs can be accelerated to energies of several tens of MeV within 5–10 solar radii (5% of the Sun–Earth distance) and can reach Earth in a few minutes in extreme cases.

In March 2021, NASA reported that scientists had located the source of several SEP events, potentially leading to improved predictions in the future.

By studying SEP's isotopic composition, scientists can indirectly measure the material that formed the solar system.

This visualization of particle acceleration across a shock is a simplified representation of shock drift acceleration showing the motion of electrons (yellow) and protons (blue).
Animation of NASA's STEREO coronagraph during a coronal mass ejection followed by solar energetic particles