Satellite-based measurements of gravity wave-induced midlatitude plasma density perturbations

Large amplitude anticorrelated wave structures appear at midlatitudes in the nighttime ionospheric plasma and neutral density measurements made at altitudes between 250 and 300 km by the Dynamics Explorer-2 satellite. The wavelengths along the satellite orbit track are generally longer than a hundred kilometers, and the vertical perturbation velocities are about 20 m/s. These characteristics are consistent with plasma motions driven by gravity waves in the neutral atmosphere as they propagate upward from lower atmospheric source regions. The altitude and the horizontal wavelengths observed provide in situ empirical validation of a recently developed gravity wave propagation model that includes the effects of both kinematic viscosity and thermal diffusivity at high altitudes.