Statistics of large impulsive magnetic events in the auroral zone

Abstract

Impulsive geomagnetic variations, latitudinally localized to the auroral zone, have been observed from 2015 to 2020. These impulsive events have been observed mostly in the pre-midnight sector as upward vertical perturbations. Diurnal variations in geomagnetically-triggered harmonic distortion events observed in Hydro-Québec’s Système de Mesure de Décalage Angulaire (SMDA) synchrophasor measurement system found to have a peak in the number of events around midnight. This was similar to diurnal rates of negative Bz geomagnetic impulsive events observed at nearby auroral zone magnetometers. Superposed epoch analysis demonstrates the impulses are regularly associated with increases in harmonic distortion observed at a nearby substation transformer. These large impulsive vertical geomagnetic perturbations appear to be local vortical ionospheric disturbances.