No abstract

No abstract

DE‐1 hot plasma observations in the mid‐altitude polar cusp have shown evidence of a significant velocity filtering phenomenon which is consistent with a latitudinally narrow region of plasma injection located at a geocentric distance of about 8 RE (in a dipole approximation). Plasma convection from the injection region into the polar cap results in a ‘V’‐shaped log E vs. αo relation at geocentric distances near 4 RE. This velocity filtering effect allows the measurement of much smaller flow velocities (∼10 km/s) than have heretofore been possible with hot plasma measurements. The flows thus determined are consistent with ionospheric flows measured nearly simultaneously by the DE‐2 spacecraft, although the magnitudes of the higher altitude flows are higher by a factor of 2 or more than an ∼r3/2 dipole‐field mapping would predict.

The conditions necessary for the production of gyrophase bunched ions at the bow shock are developed. The conditions are applied to the reflection mechanism presented by Paschmann et al. (1980), showing that when in their model a portion of the incident parallel velocity is converted into reflected perpendicular velocity, the reflected particles are gyrophase bunched. The growth of velocity space structure in the gyrophase bunched distribution through gyrophase mixing is also explored. The structure is found to be similar to that reported in diffuse and dispersed ion events. This together with the close correlation of the observation of gyrophase bunched ions with diffuse and dispersed ions has led us to speculate that these two populations may be closely related.

No abstract