Coupling between thermospheric gravity waves and non-migrating tides simulated by the Whole Atmosphere Model

Abstract

The signatures of gravity waves (GWs) are often observed at ionospheric and thermospheric (IT) heights in satellite and ground-based observations. They play an important role in coupling different regions of the Earth’s atmosphere, as they transport energy and momentum and are often observed during both geomagnetically quiet and active times. GWs at IT heights can either be of meteorological origin propagating up from the lower atmosphere, or excited in-situ. They can also non-linearly interact with tides and planetary waves adding to the dynamic variability of the thermosphere. In this study, we aim to investigate the coupling between non-migrating thermospheric tides and GWs during geomagnetically quiet times using the high-resolution whole atmosphere model (WAMT254) and satellite observations. We find that when observed at a constant local time in the lower and upper thermosphere, a wavenumber-4 longitudinal signature is present in the GW activity at low-latitudes. This signature moves eastward with local time and is more prominent during September between ~6-12 LT. Diagnostics of the background zonal winds indicate a modulation of GWs by wave-4 signal of non-migrating tides. We provide the first evidence of this modulation and discuss the coupling mechanisms using the Model for Acoustic and Gravity wave Interactions and Coupling (MAGIC). We also show that similar inferences can be made from ICON satellite observations within reasonable uncertainty.