On gravity wave induced Brunt‐Vaisala oscillations

Airglow oscillations (mostly 5577‐Å oxygen emission) which show a short‐period (4–10 min) oscillation superimposed on a long‐period oscillation (several hours) have frequently been observed. Some data show that the short‐period oscillation is ‘excited’ by the long‐period oscillation as the latter increases in amplitude. The effects often occur in the absence of impulsive energy sources. We propose a model in which the short‐period oscillation is relatively localized and is associated with the natural (Brunt‐Vaisala) oscillation of the atmosphere. This oscillation is triggered off by a long‐period gravity wave through parametric excitation and nonlinear coupling.