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We investigate the possibility that sufficiently large electric fields and/orionization during geomagnetic disturbed conditions may invalidate theassumptions applied in the retrieval of neutral horizontal winds from meteorand/or lidar measurements. As per our knowledge, the possible errors in thewind estimation have never been reported. In the present case study, we havebeen using co-located meteor radar and sodium resonance lidar zonal windmeasurements over Andenes (69.27$^{\circ}$N, 16.04$^{\circ}$E) during intensesubstorms in the declining phase of the January 2005 solar proton event (21-22January 2005). In total, 14 h of measurements are available for the comparison,which covers both quiet and disturbed conditions. For comparison, the lidarzonal wind measurements are averaged over the same time and altitude as themeteor radar wind measurements. High cross correlations ($\sim$0.8) are foundin all height regions. The discrepancies can be explained in light ofdifferences in the observational volumes of the two instruments. Further, weextended the comparison to address the electric field and/or ionization impacton the neutral wind estimation. For the periods of low ionization, the neutralwinds estimated with both instruments are quite consistent with each other.During periods of elevated ionization, comparatively large differences arenoticed at the highermost altitude, which might be due to the electric fieldand/or ionization impact on the wind estimation. At present, one event is notsufficient to make any firm conclusion. Further study with more co-locatedmeasurements are needed to test the statistical significance of the result.

A preliminary comparison of Na lidar and meteor radar zonal winds during geomagnetic quiet and disturbed conditions