ИСТИНА

An analysis of positive ionospheric storms was performed in the dayside region of the equatorial ionization anomaly on the declining phase of solar activity in 2004 to 2008. We revealed so-called recurrent ionospheric storms (RIS) consisted in an increase of total electron content (TEC) during recurrent geomagnetic storms (RGS). RISs peaked 3 to 4 days after the RGS onset, i.e. on the recovery phase, during high-intensity long-duration continuous auroral activity produced by high-speed solar wind streams. The response of RISs to solar, heliospheric and geomagnetic drivers revealed a prominent longitudinal variation. Most intense RISs in response to heliospheric and geomagnetic drivers were found in the longitudinal ranges from 90° to 180° and from –180° to –120°. The highest correlations for RISs exhibit a prominent annual asymmetry with maximum during the winter season. An analysis of electron content vertical profiles, derived from two independent methods using ionosondes and COSMIC/FORMOSAT-3 radio occultation, shows that in the maximum of RIS, the F2 layer is thickening, NmF2 increases by ~50% and hmF2 elevates by a few tens of kilometers. The thermosphere and magnetosphere are considered as sources in generation of RISs.