Published online by Cambridge University Press: 27 October 2009
Polar-glow aurora is a diffuse type of polar-cap event that follows bombardment of the auroral ionosphere with high-energy protons from ‘cosmic ray’ flares at times of great solar and geomagnetic activity. Observations of five polar glows are presented together with details of the circumstances surrounding their occurrence. The first three glows were associated with enhanced solar activity between 3 and 15 February 1986 and the fourth and fifth glows with enhanced solar activity between 3 December 1993 and 10 February 1994. Despite the fact that the flares associated with the latter solar outburst were much smaller than those associated with the former, both periods of solar activity showed equally marked geophysical, geomagnetic, and auroral activity.