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Superposed Epoch Analysis of Nighttime Magnetic Perturbation Events Observed in Arctic Canada
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  • Mark J. Engebretson,
  • Lidiya Y. Ahmed,
  • Vyacheslav A. Pilipenko,
  • Erik S. Steinmetz,
  • Mark B. Moldwin,
  • Martin Connors,
  • David H Boteler,
  • James M. Weygand,
  • Shane Coyle,
  • Shinichi Ohtani,
  • Jesper W. Gjerloev,
  • Christopher T. Russell
Mark J. Engebretson
Department of Physics, Augsburg University

Corresponding Author:[email protected]

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Lidiya Y. Ahmed
NASA/Goddard Space Flight Center
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Vyacheslav A. Pilipenko
Space Research Institute
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Erik S. Steinmetz
Department of Computer Science, Augsburg University
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Mark B. Moldwin
University of Michigan-Ann Arbor
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Martin Connors
Athabasca University
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David H Boteler
Natural Resources Canada
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James M. Weygand
Institute of Geophysics and Planetary Physics
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Shane Coyle
Virginia Tech
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Shinichi Ohtani
The Johns Hopkins University Applied Physics Laboratory
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Jesper W. Gjerloev
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Christopher T. Russell
University of California Los Angeles
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Rapid changes of magnetic fields associated with nighttime magnetic perturbation events (MPEs) with amplitudes |ΔB| of hundreds of nT and 5-10 min duration can induce geomagnetically-induced currents (GICs) that can harm technological systems. Here we present superposed epoch analyses of large nighttime MPEs (|dB/dt| ≥ 6 nT/s) observed during 2015 and 2017 at five stations in Arctic Canada ranging from 64.7° to 75.2° in corrected geomagnetic latitude (MLAT) as functions of the interplanetary magnetic field (IMF), solar wind dynamic pressure, density, and velocity, and the SML, SMU, and SYM/H geomagnetic activity indices. Analyses were produced for premidnight and postmidnight events and for three ranges of time after the most recent substorm onset: A) 0-30 min, B) 30-60 min, and C) >60 min. Of the solar wind and IMF parameters studied, only the IMF Bz component showed any consistent temporal variations prior to MPEs: a 1-2 hour wide 1-3 nT negative minimum at all stations beginning ~30 to 80 min before premidnight MPEs, and minima that were less consistent but often deeper before postmidnight MPEs. Median, 25th, and 75th percentile SuperMAG auroral indices SML (SMU) showed drops (rises) before pre- and post-midnight type A MPEs, but most of the MPEs in categories B and C did not coincide with large-scale peaks in ionospheric electrojets. Median SYM/H indices were flat near -30 nT for premidnight events and showed no consistent temporal association with any MPE events. More disturbed values of IMF Bz, Psw, Nsw, SML, SMU, and SYM/H appeared postmidnight than premidnight.
Sep 2021Published in Journal of Geophysical Research: Space Physics volume 126 issue 9. 10.1029/2021JA029465