Ion reflections from the parallel MHD termination shock and a possible injection mechanism into the Fermi-1 acceleration

Abstract

Context. The analysis with our recently developed kinetic solar wind termination shock model for a parallel magnetic field orientation has shown several interesting features of the ion distribution function at the downstream side of the magnetohydrodynamic shock. Among these results, it turned out that a certain amount of ions are provided with a velocity backwards into the shock transition layer by turbulent interaction. Aims. The behaviour of these reflected ions during their second shock transit towards the upstream side is investigated. The reflected particles become an additional ion species in the foreshock region, and their influence on the upstream plasma environment has to be studied and evaluated. Methods. Under the same shock conditions as adopted in our first paper, we treated these reflected ions kinetically with the methods of our model to solve the appropriate Boltzmann-Vlasov equation. The modified transport equation was solved with the help of stochastic differential equations. Results. The shock scenario leads to fast ion beams oriented backwards into the foreshock region. About 18% of the incoming solar wind ions are reflected and affect the upstream plasma flow. With these properties the treated processes clearly indicate an additional injection mechanism for ACRs. © 2008 ESO.