Signatures of the various regions of the outer magnetosphere in the pitch angle distributions of energetic particles

An account is given of the observations of the pitch angle distributions of energetic particles in the near equatorial regions of the earth's magnetosphere. The emphasis is on relating the observed distributions to the field configuration responsible for the observed effects. The observed effects relate to drift-shell splitting, to the breakdown of adiabatic guiding center motion in regions of sharp field curvature relative to partial gyro radii, to wave particle interactions, and to moving field configurations.