Rapid auroral luminosity fluctuations and geomagnetic field pulsations

The relationship of 4278 A emission fluctuations and rapid geomagnetic field variations during two active disturbance periods at Byrd, Antarctca, has been studied in detail. These quasi-sinusoidal pulsation data have been compared with the simultaneous field changes at the conjugate location of Great Whale River, Canada. Common spectral characteristics of the light and field were examined. A five-phototube array has been used to identify large-scale auroral pulsation events and to separate them for analysis of stationary and moving forms. For the stationary group of pulsations, the geomagnetic field changes occur about 1.3 sec later than the auroral luminosity. This delay increases with increasing E-region electron density. It is reasoned that quasi-trapped electron bouncing is not important in determining the pulsation periodicity and that the luminosity is an indicator of the ionospheric arrival of a hydromagnetic wave, which is there converted to an electromagnetic disturbance. Travel time for an electromagnetic pulse through a conducting medium is computed and is shown to be consistent with the observed delays.