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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 28, issue 4
Ann. Geophys., 28, 969–976, 2010
https://doi.org/10.5194/angeo-28-969-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 28, 969–976, 2010
https://doi.org/10.5194/angeo-28-969-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.

  15 Apr 2010

15 Apr 2010

Plasma convection jets near the poleward boundary of the nightside auroral oval and their relation to Pedersen conductivity gradients

H. Wang1,*, H. Lühr2, and A. J. Ridley3 H. Wang et al.
  • 1Dept. of Space Physics, School of Electronic Information, Wuhan University, Wuhan 430079, China
  • 2Helmholtz Centre Potsdam-GFZ, German Research Center for Geosciences, 14473 Potsdam, Germany
  • 3Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI-48109, USA
  • *also at: State Key Laboratory of Space Weather, Chinese Academy of Sciences, Beijing 100080, China

Abstract. In this work, we have shown that the ionospheric azimuthal plasma velocity jets near the open-closed field line boundary on the nightside can be associated with the peak in the ionospheric conductivity gradient. Both model and DMSP observations have been utilized to conduct this investigation. The model tests show that when the gradient of conductivity in the poleward boundary becomes sharper, convection peaks appear around the poleward edge of the aurora. The model results have been confirmed by DMSP observations. Hundreds of large ion flow events are identified from one year DMSP observations, with flow speed larger than 500 m/s that occurred poleward of the aurora. Among them, 280 (74%) events are found to be associated with conductivity gradient peaks. Most of the convection jets occur in winter when conductivity gradients are expected to be large. The convection jets tend to occur at later local times (21:00–22:00 MLT) at 70°–72° MLat. These events are preceded by increasing of the merging electric field suggesting that they occur after the expansion of the polar cap. Both observation and model results show that the conductivity gradient at the polar cap boundary are one of the important elements in establishing the convection jets.

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