Statistics of Large Impulsive Magnetic Events in the Auroral Zone

TL;DR

This study analyzes large impulsive magnetic events in the auroral zone from 2015-2020, revealing their occurrence patterns, association with harmonic distortion, and local ionospheric disturbances.

Contribution

It provides new statistical insights into impulsive geomagnetic variations, their diurnal patterns, and their impact on infrastructure in the auroral zone.

Findings

Impulsive events are mostly observed in the pre-midnight sector.

Impulses are associated with increased harmonic distortion at substations.

Large impulsive perturbations are linked to local vortical ionospheric disturbances.

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.