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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 18, issue 8
Ann. Geophys., 18, 967–971, 2000
© European Geosciences Union 2000
Ann. Geophys., 18, 967–971, 2000
© European Geosciences Union 2000

  31 Aug 2000

31 Aug 2000

On the possibility of ion-drag to induce dynamic instability in the lower thermosphere neutral gas

C. M. Hall C. M. Hall
  • Tromsø Geophysical Observatory, University of Tromsø, Norway
  • e-mail:

Abstract. Strong wind shears may result in dynamic instability, often characterised by the Richardson number lying between zero and 0.25. The extent to which electric-field driven ion flow may induce such neutral wind shears is examined. Further, it is proposed that, in the ionosphere, it is possible for electric fields to drive ion winds such that the collisionally induced neutral air response may be comparable to viscous damping of neutral motion. We shall present an analogy to the Reynolds Number Re to quantify this effect. In the same way that Re may be used to evaluate the likelihood of a flow being turbulent, the analagous metric may also indicate where in the atmosphere plasma dynamics may be strong enough to destabilise the neutral dynamics.

Key words: Ionosphere (auroral ionosphere; ionosphere-atmosphere interactions) - Meteorology and atmospheric dynamics (turbulence)

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