Simultaneous satellite and all-sky imager observations of polar cap phenomena

In order to understand the processes of formation and motion of sun-aligned polar cap arcs as well as patches, we have analyzed simultaneous observational data from Akebono (EXOS D) satellite and the all-sky imager at Qaanaaq, Greenland. The results demonstrate the correspondence between the localized electron precipitation signatures observed from Akebono and the sun-aligned arcs seen from the all-sky imager at Qaanaaq, and confirm that sun-aligned are correspond to divE<0. The average energy of precipitating electrons is in the range from 100eV to 200eV. The magnetosheath/mantle is likely the source region of the precipitating electrons. For patches, most drifted anti-sunward, but some ceased to drift within the field of view of the ah-sky imager, Comparison between patch movement and the plasma convection velocity demonstrates a general consistency between them. (C) 1998 COSPAR. Published by Elsevier Science Ltd.