Unusual sudden ionospheric disturbance from solar flare of 4 November 2003

An interpretation of the nature of the sudden ionospheric disturbance in terms of response to X-ray flux enhancement in the band 1-20 Å has been made by many authors. Last decades investigations revealed presence of important qualitative distinctions in spatially temporal pattern of geomagnetic response to solar flares featuring harder radiation spectra (with quanta energies above 100 keV). These distinctions can not be adequately described by classical theory implying ionization growing on E and D ionosperic layers and intensification of Sq-current system. In this respect, solar flare on 4 November 2003 characterizing by existence of two separate (time lag ~45 min) spectral maximums in X-rays range (average quantum energy <100 keV) and in γ-rays range (average quantum energy >100 keV), represents convenient proving ground for study of specifics the geomagnetic response to bursts marked by different hardness. In current article, we show that this flare has a number of unusual features including specific variation of accompanying current system and magnetospheric manifestation that is observed in trapped radiation fluxes and magnetic field on geosynchronous orbit. Possible physical mechanism leading to intensification of magnetospheric-ionospheric current system is discussed.