Outer-zone electron precipitation

Measurements of energetic electrons (300 kev to 2.3 Mev) within the drift loss cone, of ELF emissions, and of the plasmapause location obtained with instruments aboard the polar satellite OV3-3 (1966-70A) are compared. A knee is found in the L-shell profile of the precipitated fluxes of outer-zone electrons, the flux decreasing toward lower latitudes. The location of the knee correlates with the morning location of the plasmapause but not with the evening location. This finding suggests that outer-zone electron precipitation is influenced by the morning (perhaps minimum) location of the plasmapause. For 3.3≤L≤4.3, electrons are preferentially precipitated in the morning hours after 0600 LT. This precipitation corresponds to the strong morning maximum in the occurrence of whistler-mode ELF emissions. Electromagnetic ELF emissions are often observed near the plasmapause where the maximum flux of precipitated electrons is observed.