ИСТИНА

Geomagnetic storms are often accompanied by increases of electron density in the F2-region of low-latitude ionosphere, so-called positive ionospheric storms. We focus on problem concerning time variations and possible causes of the positive storms, which are still poorly understood. We consider positive storm effects along with magnetospheric manifestations of geomagnetic storm. For this study we have collected more than 70 modest/major geomagnetic storms from 1999 to 2006 years and use ground-based GPS vertical total electron content (VTEC), data on the soft energetic electrons from the radiation belt observed by POES and DMSP fleets of satellites. Global ionospheric maps of VTEC and geographic maps of the radiation belts at altitude ~ 800 km were constructed. We compared the global geographic distributions and classify all the events on three groups of the effects: a) simultaneous superposed ionospheric and magnetospheric effects; b) only ionospheric effects; c) only magnetospheric effects. We showed that in the case (a) the observed ionization enhancements can be related to a mechanism of magnetospheric origin.