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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.


  1. Blix, T. A., E. V. Thrane, and ø. Andreassen, In situ measurements of the fine-scale structure and turbulence in the mesosphere and lower thermosphere by means of electrostatic positive ion probes, J. Geophys. Res., 95, 5533–5548, 1990.

    Article  Google Scholar 

  2. Fujii, R., S. Nozawa, S. C. Buchart, N. Matuura, and A. Brekke, The motion of ions in the auroral ionosphere, J. Geophys. Res., 103, 20,685–20,695, 1998.

    Article  Google Scholar 

  3. Hall, CM., An analogy to the Reynolds number for the neutral gas component of a weak plasma, Ann. Geophys., 2000 (in press).

  4. Hall, C. M. and T. Aso, Mesospheric velocities and buoyancy subrange spectral slopes determined over Svalbard by ESR, Geophys. Res. Lett., 26, 1685–1688, 1999.

    Article  Google Scholar 

  5. Hedin, A. E., Extension of the MSIS thermosphere model into the middle and lower atmosphere, J. Geophys. Res., 96, 1159–1172, 1991.

    Article  Google Scholar 

  6. Roper, R. G. and J. W. Brosnahan, Imaging Doppler interferometry and the measurement of atmospheric turbulence, Radio Sci., 32, 1137–1148, 1997.

    Article  Google Scholar 

  7. Wannberg, U. G., I. Wolf, L.-G. Vanhainen, K. Koskenniemi, J. Röttger, M. Postila, J. Markkanen, R. Jacobsen, A. Stenberg, R. Larsen, S. Eliassen, S. Heck, and A. Huuskonen, The EISCAT Svalbard Radar, a case study in modern incoherent scatter radar system design, Radio Sci., 32, 2283–2307, 1997.

    Article  Google Scholar 

  8. Weinstock, J., Vertical turbulent diffusion in a stably stratified fluid, J. Atmos. Sci., 35, 1022–1027, 1978.

    Article  Google Scholar 

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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