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Signatures of Dipolarizing Flux Bundles in the Nightside Auroral Zone
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  • Mark J. Engebretson,
  • Sean A. Gaffaney,
  • Jesus A. Ochoa,
  • Andrei Runov,
  • James M. Weygand,
  • Yukitoshi (Toshi) Nishimura,
  • Michael D. Hartinger,
  • Vyatcheslav A. Pilipenko,
  • Mark B. Moldwin,
  • Martin Connors,
  • Ian Mann,
  • Zhonghua Xu,
  • Juan V Rodriguez
Mark J. Engebretson
Department of Physics, Augsburg University

Corresponding Author:[email protected]

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Sean A. Gaffaney
Department of Physics, Augsburg University
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Jesus A. Ochoa
Department of Physics, Augsburg University
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Andrei Runov
University of California Los Angeles
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James M. Weygand
Department of Earth, Planetary, and Space Sciences
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Yukitoshi (Toshi) Nishimura
Boston University
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Michael D. Hartinger
Space Science Institute
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Vyatcheslav A. Pilipenko
Institute of Physics of the Earth
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Mark B. Moldwin
University of Michigan-Ann Arbor
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Martin Connors
Athabasca University
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Ian Mann
University of Alberta
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Zhonghua Xu
Virginia Polytechnic Institute and State University
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Juan V Rodriguez
University of Colorado
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Dipolarizing flux bundles (DFBs) have been suggested to transport energy and momentum from regions of reconnection in the magnetotail to the high latitude ionosphere, where they can generate localized ionospheric currents that can produce large nighttime geomagnetic disturbances (GMDs). In this study we identified DFBs observed in the midnight sector from ~7 to ~10 RE by THEMIS A, D, and E during days in 2015-2017 whose northern hemisphere magnetic footpoints mapped to regions near Hudson Bay, Canada, and have compared them to GMDs observed by ground magnetometers. We found six days during which one or more of these DFBs coincided within ± 3 min with ≥ 6 nT/s GMDs observed by latitudinally closely spaced ground-based magnetometers located near those footpoints. Spherical elementary current systems (SECS) maps and all-sky imager data provided further characterization of two events, showing short-lived localized intense upward currents, auroral intensifications and/or streamers, and vortical perturbations of a westward electrojet. On all but one of these days the coincident DFB – GMD pairs occurred during intervals of high-speed solar wind streams but low values of SYM/H. In some events, in which the DFBs were observed closer to Earth and with lower Earthward velocities, the GMDs occurred slightly earlier than the DFBs, suggesting that braking had begun before the time of the DFB observation. This study is the first to connect spacecraft observations of DFBs in the magnetotail to intense (>6 nT/s) GMDs on the ground, and the results suggest DFBs could be an important driver of GICs.
09 Nov 2023Submitted to ESS Open Archive
14 Nov 2023Published in ESS Open Archive