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On the Creation, Depletion, and End of Life of Polar Cap Patches
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  • Nina Kristine Eriksen,
  • Dag Lorentzen,
  • Lisa Jane Baddeley,
  • Kjellmar Oksavik,
  • Keisuke Hosokawa,
  • Kazuo Shiokawa,
  • Emma Christine Bland,
  • Larry J. Paxton,
  • Yongliang Zhang,
  • Kathryn McWilliam,
  • Tim K. Yeoman
Nina Kristine Eriksen
The University Centre in Svalbard

Corresponding Author:[email protected]

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Dag Lorentzen
University Centre in Svalbard
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Lisa Jane Baddeley
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Kjellmar Oksavik
University of Bergen
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Keisuke Hosokawa
University of Electro-Communications
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Kazuo Shiokawa
Institute for Space-Earth Environmental Research, Nagoya University
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Emma Christine Bland
The University Centre in Svalbard
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Larry J. Paxton
Johns Hopkins University
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Yongliang Zhang
The Johns Hopkins University Applied Physics Laboratory
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Kathryn McWilliam
U. Saskatchewan
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Tim K. Yeoman
University of Leicester
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Ionospheric convection patterns from the Super Dual Auroral Radar Network are used to determine the trajectories, transit times and decay rates of three polar cap patches from their creation in the dayside polar cap ionosphere to their end of life on the nightside. The first two polar cap patches were created within 12 minutes of each other and travelled through the dayside convection throat, before entering the nightside auroral oval after 104 and 92 minutes, respectively. When the patches approached the nightside auroral oval, an intensification in the poleward auroral boundary occurred close to their exit point, followed by a decrease in the transit velocity. The airglow decay rates of patches 1 and 2 were found to be ≈0.6% and ≈0.9% per minute, respectively. The third patch decayed completely within the polar cap and had a lifetime of only 78 minutes. After a change in drift direction, patch 3 had a radar backscatter power half-life of 4.23 minutes, which reduced to 1.80 minutes after a stagnation, indicating a variable decay rate. 28 minutes after the change in direction, and 16 minutes after stagnation, patch 3 completely disintegrated. We relate this rapid decay to increased frictional heating, which speeds up the recombination rate. Therefore, we suggest that the stagnation of a polar cap patch is a main determinant to whether or not a polar cap patch can exit through the nightside auroral oval.