The morphology of the IQSY auroral oval: 1. Interpretation of isoauroral diagrams

All-sky camera data from eight Alaskan stations have been used to construct isoauroral diagrams for the IQSY period. The isoauroral diagrams describe the incidence of all auroral forms, discrete auroral forms, and homogeneous arcs as a function of dipole time and latitude along the dipole 256° meridian. The major features of these diagrams show close similarities with the IGY isoauroral diagram by Davis, indicating that the pattern of auroral behavior does not change from sunspot maximum to sunspot minimum. Earlier reports of an inner auroral zone are examined and reconciled with the data presented here. It is shown that the concept of a separate inner zone of auroras is misleading, while the auroral oval model represents quite well the gross behavior of the aurora in the auroral cap.