Anisotropic fluxes of energetic particles in the outer magnetosphere

Anisotropic fluxes of energetic particles (electrons, E ≳ 50 kev; protons, E ≳ 830 kev) encountered by the satellite Explorer 33 in, and immediately adjacent to, the distant trapping region have been studied. Attention has been given to their location in the frame of reference provided by measurements of the local field. On the day side the flux is peaked at right angles to the field, whereas on the night side it is peaked along the field. Two exceptions to this rule were found, and fluxes of ‘streaming’ particles were found in the magnetosheath, immediately adjacent to the magnetopause. The observations are compared with previous ones and are discussed in the light of current theory.