Atmospheric Tidal Effects on the Zonal Mean Thermal and Dynamical Structure of the Ionosphere-Thermosphere System

Abstract:

The influences that vertically-propagating tides of lower atmosphere origin have on the dynamics, temperature, composition, and plasma structure of the ionosphere-thermosphere (IT) system continue to be revealed. Specifically, it is now recognized that dissipating tides exert significant changes in the mean state of the IT system with respect to latitude, season and solar cycle. However, the mechanisms and pathways through which this happens are not fully understood. Therefore, we utilize the National Center for Atmospheric Research Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM), forced with observationally-based tides at the model lower boundary from the Climatological Tidal Model of the Thermosphere (CTMT, from Oberheide et al. [2011]), to evaluate the different terms in the thermodynamic energy and momentum equations in order to elucidate how tidal dissipation acts to alter the mean thermal and dynamical structure of the IT. Numerical experiments are performed for all months of the year and for solar minimum, medium, and maximum conditions so as to quantify the seasonal and solar cycle variability associated with the different terms in the thermodynamic energy and momentum equations. Implications for more completely understanding prior results from Jones Jr. et al. [2014a, 2014b] concerning tidal effects on the mean neutral composition and electron density distributions are also assessed. Only select highlights of this work will be presented.

References:

Jones, M., Jr., J. M. Forbes, M. E. Hagan, and A. Maute (2014a), Impacts of vertically propagating tides on the mean state of the ionosphere-thermosphere system, J. Geophys. Res. Space Physics, 119, 2197–2213, doi:10.1002/2013JA019744.

Jones, M., Jr., J. M. Forbes, and M. E. Hagan (2014b), Tidal-induced net transport effects on the oxygen distribution in the thermosphere, Geophys. Res. Lett., 41, doi:10.1002/2014GL060698.

Oberheide, J., J. M. Forbes, X. Zhang, and S. L. Bruinsma (2011), Climatology of upward propagating diurnal and semidiurnal tides in the thermosphere, J. Geophys. Res., 116, A11306, doi:10.1029/2011JA016784.