Acoustic-gravity waves in the upper atmosphere due to a nuclear detonation and an earthquake

The large nuclear detonation low in the atmosphere over Novaya Zemlya on October 30, 1961, caused a traveling ionospheric disturbance observed widely on high-frequency radio sounders. A similar but much weaker disturbance was noted after the great Alaskan earthquake of March 1964. Both disturbances exhibit an abrupt onset traveling at speeds appropriate to sound waves above 100-km altitude and an oscillatory long-period tail. Both these properties are shown to be a characteristic of the propagation of a disturbance from a localized impulse source in an unbounded dissipationless, planar, nonrotating, gravitationally stratified isothermal neutral atmosphere. The theory for pulse propagation in such an atmosphere is developed, including a simple closed-form approximation appropriate to long-period components of the motion (i.e. periods greater than the Brunt period), which exhibit the major features of the observations.