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JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 112,
A11304,
12 PP., 2007
doi:10.1029/2007JA012384
Case for a new process, not mechanism, for cusp irregularity production
Center for Atmospheric and Space Sciences, Utah State University, Logan, Utah, USA
Air Force Research Laboratory/VSBXI, Hanscom Air Force Base, Massachusetts, USA
Air Force Research Laboratory/VSBXI, Hanscom Air Force Base, Massachusetts, USA
Plasma Physics Division, Naval Research Laboratory, Washington, D. C., USA
Department of Physics, University of Oslo, Oslo, Norway
Arctic Geophysics, University Centre in Svalbard, Longyearbyen, Svalbard, Norway
Two plasma instability mechanisms are currently thought to dominate formation of plasma irregularities in the F region high-latitude and polar ionosphere: the gradient-drift driven instability and velocity-shear driven instability. The former mechanism is accepted as accounting for structuring plasma in polar cap patches and the latter for structuring plasma in polar cap Sun-aligned arcs. Recent work has established a dominant patch formation process, involving magnetic reconnection driving strong plasma shears repeatedly observed in the cusp. Proceeding from this, we present the case for a needed new plasma structuring process (not 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 also explains previously unexplained characteristics of cusp and early polar cap patch irregularities.
Received 5 March 2007; accepted 14 August 2007; published 16 November 2007.
Citation: (2007), Case for a new process, not mechanism, for cusp irregularity production, J. Geophys. Res., 112, A11304, doi:10.1029/2007JA012384.
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