Generation process of magnetic decreases and the resulting kinetic effects on energetic particles within corotating interaction regions

[1] One-dimensional hybrid simulations are performed to examine the formation mechanism of magnetic decrease (MD) structures within corotating interaction regions (CIRs) and their effect on the energetic particle profiles associated with the shock acceleration at the CIR boundaries. As the source of MD formation, Alfven wave structures propagating in the fast solar wind, which make depressions in the magnetic field magnitude after passing through the CIR reverse shock, are taken into account. The observed MD properties of the simultaneous density and pressure enhancement are confirmed. The key process of reducing the field intensity is the incidence of Alfvenic field variations in the anisotropic plasma (P⊥ > P∥) of the reverse shock downstream. Directional changes in the magnetic field induce energy exchange between parallel and perpendicular components, leading to isotropization and adiabatic field reduction. Magnetic mirror points consequently form, where field-aligned streams further intensify and particles accumulate in MDs. The capture of particles by MDs delays the reverse shock evolution. Therefore, it is expected that MDs will reduce the CIR dimension and lower the efficiency of particle acceleration at CIR shocks.