COUNTER-STREAMING MAGNETOSHEATH IONS IN THE DAYSIDE LOW LATITUDE BOUNDARY-LAYER

Observations in the subsolar low latitude boundary layer (LLBL) during reconnection show counter-streaming suprathermal ions on rare occasions. Composition measurements for one event presented here indicate that the ions are from the magnetosheath although no similar equal energy per charge suprathermal He2+ and H+ populations were observed there. Acceleration of magnetosheath ions either across the magnetopause or in the LLBL followed by magnetic mirroring of the initially parallel suprathermal ions best explains these observations.