Magnetic moment scattering in a field reversal with nonzero B-Y component

We examine the nonadiabatic motion of charged particles in a field reversal with nonzero B-Y. We show that magnetic moment variations are organized in to three categories: (1) at small equatorial pitch angles, large magnetic m oment enhancements regardless of gyration phase, (2) at intermediate pitch angles, a prominent dependence upon phase with either magnetic moment enhan cement or damping, and (3) at large pitch angles, negligible magnetic momen t changes. This three-branch pattern of magnetic moment variations resemble s that obtained for zero B-Y, but it is here more or less developed when pa rticles enter above or below the field reversal. We investigate this effect using the centrifugal impulse model developed for zero B-Y, whereby nonadi abatic behavior is viewed as the result of perturbation of the gyromotion b y an impulsive centrifugal force. We show that nonzero B-Y leads to a rotat ion of the centrifugal impulse in the gyration plane and that the nonadiaba tic particle behavior is attenuated or enhanced when this rotation opposes or goes together with the gyromotion, respectively. As a consequence of thi s, particles with opposite charge states or originating from opposite hemis pheres behave in quite distinct manners, exhibiting for instance large or n egligible magnetic moment changes depending upon their direction of propaga tion. More generally, we demonstrate that prominent hemispherical differenc es are obtained as a result of nonzero B-Y, be it for injection inside the loss cone or gyrophase bunching near the current sheet midplane.