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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 26, issue 9
Ann. Geophys., 26, 2871–2885, 2008
https://doi.org/10.5194/angeo-26-2871-2008
© Author(s) 2008. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: 13th International EISCAT Workshop

Ann. Geophys., 26, 2871–2885, 2008
https://doi.org/10.5194/angeo-26-2871-2008
© Author(s) 2008. This work is distributed under
the Creative Commons Attribution 3.0 License.

  23 Sep 2008

23 Sep 2008

On a new process for cusp irregularity production

H. C. Carlson1,2, K. Oksavik3, and J. Moen1 H. C. Carlson et al.
  • 1Department of Physics, University of Oslo, Oslo, Norway
  • 2Utah State University, CASS, Logan, UT, USA
  • 3Arctic Geophysics, The University Centre in Svalbard, Longyearbyen, Norway

Abstract. Two plasma instability mechanisms were thought until 2007 to dominate the formation of plasma irregularities in the F region high latitude and polar ionosphere; the gradient-drift driven instability, and the velocity-shear driven instability. The former mechanism was accepted as accounting for plasma structuring in polar cap patches, the latter for plasma structuring in polar cap sun aligned arcs. Recent work has established the need to replace this view of the past two decades with a new patch plasma structuring process (not a new mechanism), whereby shear-driven instabilities first rapidly structure the entering plasma, after which gradient drift instabilities build on these large "seed" irregularities. Correct modeling of cusp and early polar cap patch structuring will not be accomplished without allowing for this compound process. This compound process explains several previously unexplained characteristics of cusp and early polar cap patch irregularities. Here we introduce additional data, coincident in time and space, to extend that work to smaller irregularity scale sizes and relate it to the structured cusp current system.

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