The Magnetopause Electron Layer along the Distant Magnetotail

An energetic electron layer is found Observations immediately adjacent to, and outside of, the magnetopause surface along the distant magnetotail The observed bow shock and magnetopause cross(-40 • X <•-15 RE). The layer has been detected ings during one orbit are shown by dashed, curved using Ca•ech instrumentation aboard the earthlines drawn o the trajectory plot in Figure 1. orbiting spacecraft IMP-8 and is observed for Note that the spacecraft was very near the magneelectrons with energies E • 200 keV. The present topause boundary from late on day 343 until the study shows that such electrons form a layer latter portion of day 346. We observed that at ~ 3 R E thick and are strongly streaming in a well~ 0900 UT on day 343 the intensity of electrons ordered pattern, especially along the dusk magne' (E • 200 keV) rose sharply from a background topause. The energy dissipation implied by the flux of•< 10-1(cm2-sec-sr) -1 to • 5 (cm-se1⁄2-sr) -1. persistent flow may be a direct indication of The spacecraft was at O ~ 29 R• (O =•y2 + Z 2 ) at the time of the flux increase%which was at AO nearly continuous magnetic merging at or near the magnetopause.