Statistics of Large Impulsive Magnetic Events in the Auroral Zone

Abstract

Impulsive geomagnetic variations, latitudinally localized to the auroral zone, have been observed over the period from 2015-2020. 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-Qu\'ebec's Syst\`eme de Mesure de D\'ecalage Angulaire (SMDA) synchrophasor measurement system have been found to have a peak in the number of events around midnight. This was similar to diurnal rates of occurrence of negative $B_z$ 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.