Nonacoustic wave disturbances in the midlatitude ionosphere

Long-period (60-90 min) disturbances of nonacoustic origin, propagating toward the equator with velocities greater than 1 km/s, have been observed during magnetic storms and substorms in the ionosphere. These disturbances are found to accompany wave disturbances that are identified with acoustic-gravity waves. The nonacoustic wave disturbances are accompanied by wave variations of the geomagnetic field, propagating predominantly toward the southwest with velocities of 1-10 km/s. Short-period (0.5-10 min) nonacoustic disturbances, measured in the Tbilisi region, have been correlated with Pc3-5 and Pi2 magnetic pulsations.