Non-shock diffusive acceleration in regions of solar-wind compression

We investigate the acceleration of charged particles in regions of solar-wind compression in the absence of shocks. The mechanism we describe is essentially the same as diffusive shock acceleration, except that here we show that a gradual compression of the plasma, rather than a shock, can efficiently accelerate the particles. Our method is to integrate the trajectories of an ensemble of test particles moving in synthesized electromagnetic fields, which are similar to what is currently known about corotating interaction regions. We show that compression regions at 1 AU, with widths ∼0.03 AU can accelerate particles up to ∼10 MeV.