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Transpolar arcs observed simultaneously in both hemispheres

Research output: Contribution to Journal/MagazineJournal articlepeer-review

  • J. A. Carter
  • S. E. Milan
  • R. C. Fear
  • M. T. Walach
  • Z. A. Harrison
  • L. J. Paxton
  • B. Hubert
<mark>Journal publication date</mark>06/2017
<mark>Journal</mark>Journal of Geophysical Research: Space Physics
Issue number6
Number of pages14
Pages (from-to)6107-6120
Publication StatusPublished
Early online date19/05/17
<mark>Original language</mark>English


Two coexisting transpolar arcs are observed on 31 August 2005. We track the formation and motion of the arcs in both the Northern and Southern Hemispheres, using data from two independent satellites (Imager for Magnetopause to Aurora Global Exploration and a Defence Meteorological Satellite Program satellite). The observations are supported by supplementary ground-based ionospheric convection data from the Super Dual Auroral Radar Network. The two arcs form during a period of northward interplanetary magnetic field. Following a change in the direction of the interplanetary magnetic field BY component from negative to positive, the dawnside arc traverses the polar cap to the duskside in the Northern Hemisphere. Over the same time period and in the Southern Hemisphere, the duskside arc traverses the polar cap to the dawnside. A complex magnetic field line topology resulting in the coexistence of two tongues of closed field lines protruding into the otherwise open polar cap is implied. We discuss these observations in terms of magnetic conjugacy and a model of transpolar arcs formation.