Correlations between PiB type magnetic micropulsations, auroras and equivalent current structures during two isolated substorms

Abstract A detailed analysis of auroral and magnetic observations made during two substorms shows that the bursts of irregular magnetic pulsations called PiB ' s are generated at the time of auroral intensification. At the same time a localized (small scale) upward directed field aligned current (FAC) develops. The generation of PiB magnetic pulsations is not well understood but we propose that they are due to fluctuations of a localized upward going FAC. The fluctuations may be caused by the inherent variations of a double layer occurring as a consequence of the FAC.

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