High resolution measurements of the widths of narrow auroral arcs in the atomic oxygen green line and N2+ first negative emissions

The anomalous inequality in the spatial extents of the OI 557.7 nm and N₂⁺ 391.4 nm emissions in auroral arcs was investigated by means of a ground-based low-light T.V. system. First reported in 1967 by Romick and Belon, this anomalous distribution has been the source of some controversy and also subsequent attempts to observe it have produced conflicting results. It is shown that for a simplified geometrical situation, when sufficient spatial and temporal resolution is used, the anomaly is not seen.