ИСТИНА

We studied ionization effects produced by X-class solar flares in the ionosphere, so-called solar flare effects (SFE). The SFE is identified as flare-associated variations of the geomagnetic field observed by INTERMAGNET worldwide network of ground-based magnetometers. It was found that strong x- and gamma- ray solar flares are accompanied by global magnetic variations, which are observed both at sunlit and night hemispheres. Most prominent magnetic effect is observed in vicinity of subsolar meridian at geomagnetic equator, i.e. in the region of strongest eastward electrojet. On the other hand, solar flares produce direct ionization mainly in the subsolar region, which can stand out up to 30 degrees from the geomagnetic equator. The SFE-related ionospheric ionization was studied by using height profiles of electron content (EC) derived from FORMOSAT-3/COSMIC radio occultation measurements. During solar flares, we found EC enhancements in the subsolar region at altitudes from 100 to 200 km, below the bulges of the equatorial ionization anomaly. In addition, we found prominent ionization enhancements near the geomagnetic equator at altitudes of ~150 to 200 km. The origin of SFE-related ionization enhancements in the equatorial ionosphere is discussed.