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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 27, issue 2
Ann. Geophys., 27, 591–600, 2009
https://doi.org/10.5194/angeo-27-591-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Ninth International Conference on Substorms (ICS9)

Ann. Geophys., 27, 591–600, 2009
https://doi.org/10.5194/angeo-27-591-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.

  06 Feb 2009

06 Feb 2009


Superposed epoch analysis of the ionospheric convection evolution during substorms: onset latitude dependence

A. Grocott1, J. A. Wild2, S. E. Milan1, and T. K. Yeoman1 A. Grocott et al.
  • 1Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK
  • 2Department of Communication Systems, InfoLab21, Lancaster University, Lancaster, LA1 4WA, UK

Abstract. Using data from the Super Dual Auroral Radar Network (SuperDARN) we investigate the ionospheric convection response to magnetospheric substorms. Substorms were identified using the Far Ultraviolet (FUV) instrument on board the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft, and were then binned according to the magnetic latitude of their onset. A superposed epoch analysis of the ionospheric convection patterns for each onset-latitude bin was then performed using radar data for the interval 60 min before onset to 90 min after. It is found that lower onset-latitude substorms are associated with generally more enhanced convection than the higher latitude substorms, although they suffer from a significant localised reduction of the flow in the midnight sector during the expansion phase. Higher-latitude substorms are associated with a significant and rapid increase in the nightside convection following substorm onset, with all onset-latitude bins showing an enhancement over onset values by ~60 min into the expansion phase. A rudimentary inspection of the concurrent auroral evolution suggests that the duration of the flow reduction following substorm onset is dependent on the strength and duration of the expansion phase aurora and its associated conductivity enhancement.

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