Large amplitude thermospheric oscillations induced by an earthquake

Abstract

Large amplitude long period vertical oscillations of the thermosphere were detected over Chatanika, Alaska, just after an earthquake. The oscillations continued for at least nine hours. The earthquake registered 5.8 on the Richter scale, and its epicenter was about 1000 km from the observing site. The vertical velocity of the atmosphere was determined via incoherent scatter measurements of the plasma velocity parallel to the earth's magnetic field, and at times exceeded 100 m/s in the 300 to 450 km height range. Analysis of the oscillation frequency and its relation to the Brunt‐Vaisala frequency yields reasonable agreement with the theory for such a process [Row, 1967], although the indicated exospheric neutral gas temperature is on the high side of expected values. There is some evidence that the upper thermosphere may have been viscously heated by the oscillations, which may explain the high temperature.