Some features of magnetic storms in high latitudes

During a severe magnetic storm, observatory records obtained in high latitudes may show a type of disturbance here called a ‘cusped bay,’ characterized by a marked displacement of the trace, coupled with augmented short-period fluctuations. Several of these events registered during the IGY at stations near the northern and southern auroral zones, some with amplitudes approaching 2000 γ, were measured on all appropriate magnetograms and plotted on maps as equivalent overhead current vectors. They show some of the characteristics of systems based on hourly-value changes during storms. However, they afford almost no evidence of the afternoon eastward segment of the auroral electrojet, and the polar-cap effects are indicative of patterns having greater complexity than the one usually ascribed to this region. The author recommends the study of cusped bays as a supplement to the use of hourly values and a means of probing details of magnetic activity that are difficult to approach in other ways. A catalog of IGY storms is appended to the paper. This article contains supplementary material.