First results of meteor radar lower thermosphere wind measurements at Dixon, Arctic (73.5゜N, 80゜E)

Results of simultaneous wind measurements by the identical meteor radars at Dixon (73.5°N, 80°E) and Obninsk (55°N, 37°E) are presented for the time interval from November 12, 1999 to July 31, 2000. A number of features were observed which require comprehensive investigation on the basis of long-term wind measurements in the high-latitude lower thermosphere. The observed semidiurnal tide phases at Dixon are close to those published for Troms0, providing some evidence for predominance of the migrating semidiurnal tide for semidiurnal oscillations at this latitude. Highly coherent oscillations in tidal amplitudes and prevailing winds were also revealed, as well as time intervals with non-significant semidiurnal tide during which oscillations with periods different from but close to 12 h were observed

The summertime 12-h wind oscillation with zonal wavenumber <i>s</i> = 1 in the lower thermosphere over the South Pole

International audienceMeteor radar measurements of winds near 95 km in four azimuth directions from the geographic South Pole are analyzed to reveal characteristics of the 12-h oscillation with zonal wavenumber one (s=1). The wind measurements are confined to the periods from 19 January 1995 through 26 January 1996 and from 21 November 1996 through 27 January 1997. The 12-h s=1 oscillation is found to be a predominantly summertime phenomenon, and is replaced in winter by a spectrum of oscillations with periods between 6 and 11.5 h. Both summers are characterized by minimum amplitudes (5?10 ms?1) during early January and maxima (15?20 ms?1) in November and late January. For 10-day means of the 12-h oscillation, smooth evolutions of phase of order 4?6 h occur during the course of the summer. In addition, there is considerable day-to-day variability (±5?10 ms?1 in amplitude) with distinct periods (i.e., ~5 days and ~8 days) which suggests modulation by planetary-scale disturbances. A comparison of climatological data from Scott Base, Molodezhnaya, and Mawson stations suggests that the 12-h oscillation near 78°S is s=1, but that at 68°S there is probably a mixture between s=1 and other zonal wavenumber oscillations (most probably s=2). The mechanism responsible for the existence of the 12-h s=1 oscillation has not yet been identified. Possible origins discussed herein include in situ excitation, nonlinear interaction between the migrating semidiurnal tide and a stationary s=1 feature, and thermal excitation in the troposphere