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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 18, issue 5
Ann. Geophys., 18, 532–546, 2000
https://doi.org/10.1007/s00585-000-0532-x
© European Geosciences Union 2000
Ann. Geophys., 18, 532–546, 2000
https://doi.org/10.1007/s00585-000-0532-x
© European Geosciences Union 2000

  31 May 2000

31 May 2000

The role played by thermal feedback in heated Farley-Buneman waves at high latitudes

J.-P. St.-Maurice and R. S. Kissack J.-P. St.-Maurice and R. S. Kissack
  • Department of Physics and Astronomy, The University of Western Ontario, London, Ontario N6A 3K7, Canada
  • Correspondence to: J.-P. St.-Maurice

Abstract. It is becoming increasingly clear that electron thermal effects have to be taken into account when dealing with the theory of ionospheric instabilities in the high-latitude ionosphere. Unfortunately, the mathematical complexity often hides the physical processes at work. We follow the limiting cases of a complex but systematic generalized fluid approach to get to the heart of the thermal processes that affect the stability of E region waves during electron heating events. We try to show as simply as possible under what conditions thermal effects contribute to the destabilization of strongly field-aligned (zero aspect angle) Farley-Buneman modes. We show that destabilization can arise from a combination of (1) a reduction in pressure gradients associated with temperature fluctuations that are out of phase with density fluctuations, and (2) thermal diffusion, which takes the electrons from regions of enhanced temperatures to regions of negative temperature fluctuations, and therefore enhanced densities. However, we also show that, contrary to what has been suggested in the past, for modes excited along the E0×B direction thermal feedback decreases the growth rate and raises the threshold speed of the Farley-Buneman instability. The increase in threshold speed appears to be important enough to explain the generation of `Type IV' waves in the high-latitude ionosphere.

Key words: Ionosphere (auroral ionosphere; iono- spheric irregularities; plasma waves and instabilities)

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