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Dual-lobe reconnection and cusp-aligned auroral arcs
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  • Stephen E. Milan,
  • Gemma E. Bower,
  • Jennifer Alyson Carter,
  • Larry J. Paxton,
  • Brian J. Anderson,
  • Marc R. Hairston
Stephen E. Milan
University of Leicester

Corresponding Author:[email protected]

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Gemma E. Bower
University of Leicester
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Jennifer Alyson Carter
University of Leicester
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Larry J. Paxton
Johns Hopkins University
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Brian J. Anderson
John Hopkins Univ.
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Marc R. Hairston
University of Texas at Dallas
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Abstract

Following the St. Patrick’s Day (17 March) geomagnetic storm of 2013, the interplanetary magnetic field had near-zero clock angle for almost two days. Throughout this period multiple cusp-aligned auroral arcs formed in the polar regions; we present observations of, and provide a new explanation for, this poorly-understood phenomenon. The arcs were observed by auroral imagers onboard satellites of the Defense Meteorological Satellite Program (DMSP). Ionospheric flow measurements and observations of energetic particles from the same satellites show that the arcs were produced by inverted-V precipitation associated with upward field-aligned currents at shears in the convection pattern. The large-scale convection pattern revealed by the Super Dual Auroral Radar Network (SuperDARN) and the corresponding FAC pattern observed by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) suggest that dual-lobe reconnection was ongoing to produce significant closure of the magnetosphere. However, we propose that once the magnetosphere became nearly closed complicated lobe reconnection geometries arose that produced interleaving of regions of open and closed magnetic flux and spatial and temporal structure in the convection pattern that evolved on timescales shorter than the orbital period of the DMSP spacecraft.