Midlatitude ionospheric temperatures on magnetically quiet and disturbed days

Introduction. In recent years it has become possible to deduce the temperature of the neutral constituent of the upper atmosphere (at heights above about 300 km) by observing the changes in the orbital period of artificial earth satellites. Increases in temperature coincident with geomagnetic storms have been reported by Jacchia [1959, 1960, 1963], Groves [1960], and Jacchia and Slowey [1962a, b, 1963]. During intense storms Jacchia and Slowey [1963, 1964a] have shown that the neutral temperature TN increases by about 1°K for each unit increase in the three-hour magnetic index ap and that the heating is most intense in the auroral zones.