Significance of Semiannual Waves in the Mesospheric Zonal Wind and Evidence of Influence by the Geomagnetic Field
CONTROL DATA CORP MINNEAPOLIS MN RESEARCH DIV
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The recently described polar semiannual oscillations in zonal wind can explain midwinter weakening of the polar winter vortex and the relatively short stratospheric and mesospheric summer easterlies. This explanation implies that stratospheric sudden warmings may be caused or affected by the polar semiannual oscillation. Two potential physical mechanisms not mutually exclusive for the oscillation are presented planetary wave action and changes in the radiation field. Radiation absorption changes are suggested to result from changes in ozone concentration during magnetic storms. Contours of amplitude of both the polar and tropical semiannual wind oscillations are more nearly congruent with geomagnetic than with geographic latitude.