Surname: Sharma
First Name: Niranjan
Status= studentyes
Institution: University of Colorado at Boulder
E-mail: sharma@colorado.edu
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Title: 
Intradiurnal Oscillations in the Mesosphere and Lower Thermosphere
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Authors: 
Niranjan R. Sharma
Jeffrey M. Forbes
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Abstract: 
Intradiurnal oscillations with periods between about 6 and 11 hours have
been observed by various researchers in the mesosphere and lower
thermosphere (MLT) over South Pole.  Oscillations in the wind field have
been interpreted as gravitational normal modes, or Lamb Waves, and those
in temperature and airglow intensity as zonally symmetric tides.  In the
present work, the Global Scale Wave Model is utilized to simulate the
global structures of these oscillations, and to evaluate the effects of
mean winds on their accessibility to the polar MLT regions.  The seasonal
dependence of the zonal mean winds for wave propagation is found to
produce significant reductions in the amplitudes of intradiurnal
oscillations over the polar regions during summer months. This comes
about through coupling into other modes which modify the total response to
accomodate distortion by the mean wind field. In addition, much smaller
wind amplitudes are found for eastward vs. westward propagating waves over
the polar regions.  Both of these numerical results are in agreement with
the observations over South Pole.


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Discipline Category: Mesosphere
Discipline Category: Thermosphere