Dynamics of auroral belt and polar geomagnetic disturbances

Abstract

Using IGY-IGC all-sky camera films from many stations, the width and location of the auroral belt are determined. The positions of the edges are defined, at 15-min intervals, for different times of the day and compared with the Q-index of magnetic activity on the night side of the Earth.The dynamics of the auroral belt and the general morphology, including the rate of displacement of the northern and southern edges, the change in the belt width and the asymmetry of aurorae on the night-day and morning-evening sides of the Earth, are discussed in connection with variations in the geomagnetic activity. The probability of a discontinuous auroral belt during weak magnetic disturbances is considered. The auroral distribution around midnight, during magnetically calm periods, is analysed and it is shown that, during both the IGY and IQSY, aurorae always appear at 70° geomagnetic latitude. Variations in the azimuths of extended forms, for each of the 24 hr, are obtained and it is shown that the daily variations of the azimuths are determined by the shape of the auroral belt.The decrease of asymmetry of the auroral belt with increasing magnetic disturbance results in variations of the observed azimuths.A global schematic diagram, to illustrate the development of an auroral substorm, which is a generalization of the scheme proposed by Akasofu for the night side of the Earth, is given.