Polar auroral arc studies particularly using Akebono satellite and Qaanaaq (Greenland) all-sky imager data

Auroral arcs observed at very high latitudes have traditionally been called 'high latitude arcs' or 'polar cap arcs' or 'polar arcs' and have received much attention during the last two decades. In this article we initially examine the terminologies given for high latitude polar arc phenomena to have a reasonable view. We next review the observational signatures of 'polar arcs' paying particular attention to their more dynamical meso-scale features. Then, we will demonstrate recent progress, based on Akebono (EXOS-D) observations together with simultaneous all-sky imager observations, on issues which have remain unanswered. We lastly emphasize the importance of polar arc phenomena in understanding basic magnetospheric processes during northward IMF conditions, and discuss future work.