Oscillations in Drifts of Auroral Patches

Abstract

On the basis of all-sky TV records of auroras, faint auroral patches (nonpulsating in luminosity) are found to oscillatorily drift associated with concurrent magnetic pulsations on the ground. These oscillations in the drifts of auroral patches are found to be consistent with the oscillations in the electrostatic electric field associated with the concurrent magnetic pulsations. This implies that these magnetic pulsations are brought forth by ionospheric electric currents which are produced by electrostatic electric fields associated with shear Alfven waves in the magnetosphere. The result, therefore, indicates that the simultaneous measurement of the drifts of auroral structures at the time of ground magnetic pulsations is a convenient method of examining whether the magnetic pulsations are really ascribed to HM wave fields propagating down from the magnetosphere, or if they are essentially caused by the change in conductivity inhomogeneity in the ionosphere. It is also shown that the azimuthal phase speed (wave length), as well as the oscillation amplitude, highly varies from the dayside to the evening, i. e., it is larger in the dayside and becomes much smaller toward the evening sectors. Theory must take this steep longitudinal non-uniformity into consideration.