THE RESPONSE OF THE THERMOSPHERIC DE'^SITY TO AURORAL HEATING DURING GEOMAGNETIC DISTURBANCES

Assuming an impulse type heat input into a small band of latitude within the aurora ovals during local night; which shall simulate a heat input during geomagnetic disturbances, the corresponding response of the thermospheric density has been calculated. The result in terms of a. series of upherical harmonics shows that the components with large wave domain numbers (n, m) decay rapidly within the first hour after the onset of the geomagnetic storm while the two zonal components (0, 0) and (2, 0) and the two associated components (1, 1) and (3, 1) are predominant during the slow tail phase of the disturbance. It is that slow tail of the density disturbance beginning about one hour after the onset of the storm which contains most of the spectral energy and which is responsible for the observed world wide response of the thermospheric density during geomagnetic storms. Its dependence on storm time, latitude and longitude is discussed and compared with available satellite drag data.