Centrifugal trapping in the magnetotail

Particles leaving the neutral sheet in thedistant magnetotail at times display adiabatic trajectory sequencescharacterized by an inflection toward the equator and subsequent mirroring inits vicinity. We demonstrate that this low-latitude mirroring results primarilyfrom a centrifugal deceleration due to the fast direction-changing E×Bdrift. This effect which we refer to as "centrifugal trapping" appearsboth in guiding centre and full particle treatments. It thus does not directlyrelate to nonadiabatic motion. However, pitch angle scattering due tononadiabatic neutral sheet interaction does play a role in reducing the parallelspeed of the particles. We show that centrifugal trapping is an importantmechanism for the confinement of the slowest (typically below the equatorial E×Bdrift speed) plasma sheet populations to the midplane vicinity