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  Evolution of Asymmetrically Displaced Footpoints During Substorms

Ohma, A., Østgaard, N., Reistad, J. P., Tenfjord, P., Laundal, K. M., Snekvik, K., et al. (2018). Evolution of Asymmetrically Displaced Footpoints During Substorms. Journal of Geophysical Research: Space Physics, 123(12), 10,030-10,063. doi:10.1029/2018JA025869.

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Item Permalink: http://hdl.handle.net/21.11116/0000-0003-9F2D-9 Version Permalink: http://hdl.handle.net/21.11116/0000-0003-9F2E-8
Genre: Journal Article

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 Creators:
Ohma, A., Author
Østgaard, N., Author
Reistad, J. P., Author
Tenfjord, P., Author
Laundal, K. M., Author
Snekvik, K., Author
Haaland, Stein1, Author              
Fillingim, M. O., Author
Affiliations:
1Department Planets and Comets, Max Planck Institute for Solar System Research, Max Planck Society, ou_1832288              

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 Abstract: It is well established that a transverse (y) component in the interplanetary magnetic field (IMF) induces a By component in the closed magnetosphere through asymmetric loading and/or redistribution of magnetic flux. Simultaneous images of the aurora in the two hemispheres have revealed that conjugate auroral features are displaced longitudinally during such conditions. Although the direction and magnitude of this displacement show correlations with IMF clock angle and dipole tilt, single events show large temporal and spatial variability of this displacement. For instance, we know little about how the displacement changes during a substorm. A previous case study demonstrated that displaced auroral forms, associated with the prevailing IMF orientation, returned to a more symmetric configuration during the expansion phase of two substorms. Using the far ultraviolet cameras on board the Imager for Magnetopause‐to‐Aurora Global Exploration and Polar satellites, we have identified multiple events where conjugate auroral images are available during periods with substorm activity and IMF By≠0. We identify conjugate auroral features and investigate how the asymmetry evolves during the expansion phase. We find that the system returns to a more symmetric state in the events with a clear increase in the nightside reconnection rate and that the displacement remains unchanged in the events with little or no net closure of open magnetic flux. The return to a more symmetric state can therefore be interpreted as the result of increased reconnection rate in the magnetotail during the expansion phase, which reduces the asymmetric lobe pressure.

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Language(s): eng - English
 Dates: 2018
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1029/2018JA025869
 Degree: -

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Title: Journal of Geophysical Research: Space Physics
  Other : JGR-A
  Abbreviation : J. Geophys. Res. - A
Source Genre: Journal
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Publ. Info: Washington, D.C. : American Geophysical Union
Pages: - Volume / Issue: 123 (12) Sequence Number: - Start / End Page: 10,030 - 10,063 Identifier: ISSN: 0148-0227
CoNE: https://pure.mpg.de/cone/journals/resource/991042728714264