Acceleration of Anomalous Cosmic Rays at the termination shock

Anomalous Cosmic Rays (ACRs) are thought to be produced at the termination shock by diffusive shock acceleration. When Voyager 1 crossed the termination shock in 2004, the measured spectra did not unfold into a single continuous power law and the source of the ACRs was not observed. Further, the source of ACRs was not at the location of the termination shock where Voyager 2 passed through in 2007. This led us to believe that ACRs are accelerated either elsewhere along the shock or in the heliosheath. We use an analytic model for calculating plasma flow in the heliosphere instead of using magnetohydrodynamic simulations. A stochastic transport model is used to study the diffusive shock acceleration of Helium ACRs during solar minimum conditions.