ИСТИНА

Recurrent magnetic storms are produced by fast solar wind streams from coronal holes, which co-rotate with the Sun with ~27-day periodicity. The storms are accompanied by various ionospheric disturbances of different temporal and spatial scales and amplitudes of ~20 TECU. The scales are related to the origin of disturbances. We analyzed low-and mid-latitude ionospheric storms (both positive and negative) with 2-hour resolution by using global ionospheric maps of vertical total electron content derived from the ground based GPS network in time period from 2004 to 2009. It was found that positive ionospheric storms have largest temporal and spatial scales: the duration can exceed ten hours, latitudinal and longitudinal extensions can reach up to 40 and 120 degrees, respectively. In contrast, negative ionospheric storms have ~2 time smaller scales: duration of several hours, latitudinal and longitudinal extents of ~20 and 60 degrees, respectively. Various mechanisms resulting in different temporal and spatial scales of ionospheric storms are discussed.