A Survey of Atmospheric Gravity Waves Observed by GOLD During Quiet to Moderate Solar and Geomagnetic Activity

Abstract Atmospheric gravity waves (GWs) are believed to transport energy and momentum between different regions of the atmosphere. Historically, observations of these waves from both ground and space have been relatively abundant at altitudes up to the lower thermosphere, and somewhat less abundant in the upper thermosphere and F‐region ionosphere altitudes. Much of what is known of the typical properties and occurrence of these waves at thermospheric altitudes has been inferred from their impacts on the ionospheric density and motion, as direct observations of the neutral atmosphere have been less prevalent. Gravity waves in the middle thermosphere, from ∼120–200 km altitude, have rarely been observed directly and as such, their properties at these altitudes are less well documented. NASA's Global‐Scale Observations of the Limb and Disk (GOLD) mission makes observation of the middle thermosphere during daytime. During dedicated campaigns, GOLD has been able to observe GWs in this region. This study leverages 22 such campaigns during quiet geomagnetic conditions and low to moderate solar activity levels. Waves were observed with typical periods ∼2–4 hr. Leveraging ground‐based observations, the wavelengths were identified to be between ∼1,500–5,000 km, with phase speeds ∼150–600 m/s. The waves observed were seen to propagate primarily meridionally, in agreement with prior daytime mid‐latitude observations. Using observations of the background wind, the energy and momentum fluxes carried by these waves were found. During the quiet conditions observed, the waves were seen to transport energy flux over a wide range of latitudes.