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Nighttime magnetic perturbation events observed in Arctic Canada: Investigating their associations with localized field-aligned currents and with substorms
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  • Mark Engebretson,
  • Lidiya Ahmed,
  • Vyacheslav Pilipenko,
  • Erik Steinmetz,
  • Mark Moldwin,
  • Martin Connors,
  • David Boteler,
  • Howard Singer,
  • Brian Anderson,
  • Shinichi Ohtani,
  • Jesper Gjerloev,
  • Christopher Russell
Mark Engebretson
Augsburg University

Corresponding Author:[email protected]

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Lidiya Ahmed
Augsburg University
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Vyacheslav Pilipenko
Augsburg University
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Erik Steinmetz
Augsburg University
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Mark Moldwin
University of Michigan
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Martin Connors
Athabasca University
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David Boteler
Natural Resources Canada
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Howard Singer
NOAA-Space Weather Prediction Center
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Brian Anderson
Johns Hopkins Univ
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Shinichi Ohtani
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Jesper Gjerloev
Johns Hopkins University - Applied Physics Laboratory
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Christopher Russell
University of California Los Angeles
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The rapid changes of magnetic fields associated with nighttime magnetic perturbations with amplitudes |ΔB| of hundreds of nT and 5-10 min periods can induce bursts of geomagnetically-induced currents that can harm technological systems. Recent studies of these events in eastern Arctic Canada, based on data from four ground magnetometer arrays and augmented by observations from auroral imagers and high-altitude spacecraft in the nightside magnetosphere, showed them to be highly localized, with largest |dB/dt| values within a ~275 km half-maximum radius that was associated with a region of shear between upward and downward field-aligned currents, and usually but not always associated with substorms. In this study we look in more detail at the field-aligned currents associated with these events using AMPERE data, and compare the context and characteristics of events not associated with substorms (occurring from 60 min to over two days after the most recent substorm onset) to those occurring within 30 min of onset. Preliminary results of this comparison, based on events with |dB/dt|≥ 6 nT/s observed during 2015 and 2017 at Repulse Bay (75.2° CGMLAT), showed that the SYM/H distributions for both categories of events were similar, with 85% between -40 and 10 nT, and the SME values during non-substorm events coincided with the lower half of the range of SME values for events during substorms (200 – 700 nT). Dipolarizations of ≥ 20 nT amplitude at GOES 13 occurred within 45 minutes prior to 73% of the substorm events but only 29% of the non-substorm events. These observations suggest that predictions of GICs cannot focus solely on the occurrence of intense substorms.