Migrating thermospheric tides

The capabilities of the global-scale wave model (GSWM) [Hagan et al., 1995, 1999] are extended to include migrating thermospheric solar tides. The GSW M thermospheric tidal forcing parameterization is based on neutral gas heat ing calculated from first principles in the National Center for Atmospheric Research (NCAR) thermosphere/ionosphere electrodynamics general circulatio n model (TIE-GCM). This is the first time that a physics-based thermospheri c forcing scheme has been used in a model like GSWM. Previous two-dimension al steady state linear tidal models used exospheric temperature measurement s to calibrate upper atmospheric tidal forcing. New GSWM results illustrate thermospheric tidal responses that are largely consistent with tides in th e TIE-GCM. Diurnal temperature amplitudes increase with increasing solar ac tivity, but there is no analogous diurnal wind response. The thermospheric semidiurnal tide is much weaker than the diurnal tide. Semidiurnal temperat ure perturbations peak in the lower thermosphere where the semidiurnal forc ing maximizes. The new in situ results must be combined with the GSWM upwar d propagating tide in the lower thermosphere, because the upward propagatin g components dominate the semidiurnal response throughout the region and th e diurnal response below similar to 130 km. In situ forcing accounts for mo st of the diurnal response aloft. Our preliminary evaluation of the GSWM th ermospheric predictions is inconclusive. More extensive evaluations are nec essary to make a firm assessment of whether the model captures the salient features of the seasonal and solar cycle variability of thermospheric tides .