Particle acceleration at interplanetary shocks - Observations at a few tens of KeV vs some tens of MeV

The passage of interplanetary shocks frequently is associated with enhancements in energetic particles from supra-thermal energies up to energies of a few tens of MeV or even a hundred MeV. While these observations clearly indicate that interplanetary shocks are capable of efficient proton acceleration, the acceleration mechanism(s) are not completely understood. For the 'low energy' proton populations up to a few hundreds of keV, the observations are in good agreement with shock-drift acceleration at quasi-perpendicular and diffusive shock acceleration at quasi-parallel shocks. Both mechanisms, however, are not expected to be efficient accelerators for the higher energetic particle population. We will review observations of accelerated particles in different energy ranges, the different types of intensity profiles observed in connection with the passage of interplanetary shocks, and attempts to correlate the properties of the particle event with shock parameters to identify the crucial parameter(s) that determine the acceleration. Special attention will be paid to the similarities and differences between lower and higher energetic particles.