A Survey of Magnetic Impulse Events (MIEs) Observed by the MACCS, AUTUMNX, CANMOS, and CARISMA Magnetometer Arrays in Arctic Canada: 2014-2017

We present a statistical survey of magnetic impulse events (MIEs), isolated large-amplitude pulses with 5 - 10 min periods, recorded in eastern Arctic Canada from the subauroral zone to the polar cap by the MACCS, AUTUMNX, CANMOS, and CARISMA magnetometer arrays. Although these events are often associated with substorms or magnetic storms, we find that nearly 25% of the events with amplitude > 200 nT recorded by MACCS stations near 73° corrected geomagnetic latitude were not associated with either storms or substorms, and only 5% were associated with magnetic storms. Of the 38 events in 2015 with derivative magnitudes |dB/dt] > 10 nT/s in either the horizontal or vertical direction, 18 were associated with substorms, 6 with magnetic storms, and 18 with neither substorms nor storms. Although many studies have focused on the derivatives of the magnetic field in the horizontal direction, vertical derivative magnitudes exceeded those in the horizontal direction in over 1/3 of these events. We also present a superposed epoch analysis using the Spherical Elementary Currents System (SECS) technique of 21 nighttime MIEs observed at Cape Dorset (MACCS, 73° corrected geomagnetic latitude) between 0230 and 0330 UT between mid-2014 and the end of 2016. This analysis shows strong and highly structured electrojets and field-aligned currents overhead, and highly localized dB/dt values with a horizontal falloff scale of 400 km.