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Identification of possible ion-drag induced neutral instability in the lower thermosphere over Svalbard


The EISCAT Svalbard Radar (ESR) has been used to obtain ion velocities in the lower thermosphere. By using beam swinging and assuming homogeneity and stationarity of the plasma, first approximations to the electric field have been deduced, and thus the thermospheric neutral wind has been estimated. From these derived parameters, we have estimated the gradient Richardson Number. Although many assumptions must be made, there is an indication that electrodynamics is able to contribute to enhancement or even production of neutral-air turbulence in the lower thermosphere. Finally, we outline a proposal for an analogy to the Reynolds Number, but reflecting the relative importance’s of the contribution of ion-drag to the neutral dynamics and the kinematic viscosity.


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Correspondence to C. M. Hall.

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Hall, C.M., Aso, T. Identification of possible ion-drag induced neutral instability in the lower thermosphere over Svalbard. Earth Planet Sp 52, 639–643 (2000).

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  • Neutral Wind
  • Meridional Component
  • Lower Thermosphere
  • International Geomagnetic Reference Field
  • Incoherent Scatter Radar