Adiabatic Deceleration of Cosmic Rays during Interplanetary Magnetic Flux Rope Expansion

We have developed models to describe how the GCR density drops during a second-stage Forbush decrease when the detector is inside an interplanetary magnetic flux rope. In addition to the curvature and gradient drifts and mirroring effects on guiding center orbits in the interplanetary magnetic flux rope structure of magnetic clouds, we propose a flux rope expansion model that includes a slow, inhomogeneous radial and axial expansion. Then we derive the adiabatic deceleration of cosmic ray particles due to radial and axial expansion effects. We expect that the deceleration effect reduces the rate of recovery of the GCR flux.