Onset of a CME-Related Shock Within the Large-Angle Spectrometric Coronagraph (LASCO) Field of View

We investigated the onset of a CME-related shock within the Large-Angle Spectrometric Coronagraph (LASCO) field of view (FOV). To detect the first moment of the shock onset, we found a CME on 17 July 2012 that formed at a relatively high altitude and moved with slow acceleration. We examined the possible mechanisms of shock generation. It was shown that bow-shock and piston-shock mechanisms can participate in shock generation, either at different stages of CME movement, or simultaneously. This event has been found to be accompanied by generation of solar energetic particles (SEP). We concluded that, at their initial stage, the source of SEP fluxes may be a solar flare, while the later dramatic increase in the flux of fast protons may be due to their generation in a CME-driven shock.