OVERLAPPING ION POPULATIONS IN THE CUSP - POLAR TIMAS RESULTS/

The 90 degree inclined orbit of the Polar satellite crosses the cusp a t intermediate altitudes (4R(E)-6R(E)). The Toroidal Imaging Mass-Angl e Spectrograph (TIMAS) on the Polar spacecraft can obtain full energy/ pitch angle distributions for four masses simultaneously. Many example s of magnetosheath particle injections with velocity dispersion, somet imes overlapping, have been observed. We report on two crossings of th e cusp where TIMAS observed several overlapping cusp ion injections. T hese injections showed simultaneous onset of cusp ion precipitation at two different energies as well as the brief occurrence of ion precipi tation above and below the energy of a preexisting population. Existin g models of cusp precipitation do not provide an adequate explanation of these observations.