Transmission of planetary wave effects to the upper atmosphere through eddy diffusion modulation

Past observations have shown that the effects of planetary waves can travel beyond their dissipation region and into the thermosphere and ionosphere. One possible mechanism through which this event can occur is the modulation of turbulent mixing near the turbopause. Because turbulent mixing in the mesosphere-lower thermosphere is strongly dependent on the amount of wave dissipation, planetary wave filtering of gravity waves from below can indirectly modulate the amount of turbulent mixing. This study uses the NCAR TIE-GCM to investigate how this mechanism induces variability in upper atmospheric composition and density. It is shown that varying the amount of turbulent mixing at discrete planetary wave periods induces similar periodicities in neutral and electron density. This process is driven by species diffusive flux through isobaric (constant pressure) levels, resulting in atmospheric contraction or expansion. Results also indicate that the mechanism studied has a wave frequency dependence and is most effective for long period planetary waves. (C) 2014 Elsevier Ltd. All rights reserved.