Long period meteor wind oscillations

Abstract

Significant oscillations in the meteor wind with periods between 2 and 5 days have been found at Sheffield during several summer seasons and these appear to be linked with periodic variations of tropospheric parameters near the main meteor collecting areas. It was originally assumed that these oscillations were the result of planetary waves propagating upwards from the lowest atmospheric levels but the theory of such waves precludes direct propagation, particularly during the summer. It would appear, though, that theoretically sufficient planetary wave energy may leak upward during the autumn and winter to cause significant changes in the meteor wind patterns. Recent observations at Sheffield, however, do not show an enhancement of the amplitudes of planetary wave type oscillations at meteor heights at the beginning of the winter season although strong coupling is found between the lower and upper levels of the atmosphere. The absence of a marked seasonal effect would therefore suggest that the observed phenomena cannot be explained on the basis of the present theory of planetary waves and we would therefore propose that coupling is effected by a modulation-demodulation process involving short-period internal atmospheric gravity waves propagating obliquely to meteor heights.