Dynamics of the Mesosphere and Lower Thermosphere: Theoretical Models Interdisciplinary Investigation for TIMED

• PI: Hans G. Mayr, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (e-mail: mayr@mite.gsfc.nasa.gov)
• Co-I: Kwing L. Chan, Hong Kong University of Science and Technology, Hong Kong
• Collaborators:
  • Colin O. Hines, Hines Consultancy, Toronto, Ontario, Canada
  • John G. Mengel, Applied Research Corporation, Landover, MD
  • Hayden S. Porter, Furman University, Greenville, SC

Objective: (i) Develop theoretical models that integrate data from the TIMED mission with those from other satellites and ground based observations; (ii) provide a physical, self-consistent, quantitative description of the observations and an understanding of the phenomenology and underlying processes. Emphasis will be on the energetics and dynamics of the neutral atmosphere.

The modeling investigation will concentrate on: (i) gravity wave processes affecting the global scale and seasonal variations, (ii) variability of tides associated with planetary wave activity, (iii) thermospheric response to magnetospheric sources.

I. Numerical Spectral Model (NSM): 3-D, nonlinear, time dependent, 0-400 km altitude range. Incorporates the Doppler spread parameterization for eddy diffusion and gravity wave momentum deposition in the background flow (to be constrained with ground based observations). Latitudinal variations are formulated in terms of spherical harmonics which serves also to disseminate the results in compact form. Figures show preliminary results for seasonal variations, equatorial oscillations and diurnal tide.

Figure 1 Seasonal variations in temperature and zonal winds.

Figure 2 Zonal wind equatorial oscillations driven by small scale gravity waves.

Figure 3 Zonal wind amplitudes of diurnal tide with and without gravity wave interaction

II. Transfer Function Model (TFM): Spectral, quasi 3-D, linear, time dependent, multi-constituent, 0-700 km altitude range. Considering auroral Joule heating and electric field momentum source, transfer functions are computed in advance. For chosen source configuration, thermospheric responses in temperature, composition and wind fields are then derived virtually instantaneously, to describe the global scale variations and gravity waves, including those reflected from the Earth's surface and ducted through the lower atmosphere. Figure shows computed temperature perturbation at 300 km due to impulsive, auroral Joule heating.

Figure 4 Thermospheric temperature perturbation generated by auroral zone Joule heating.

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