THE SOLAR-FLARE RADIATION RESPONSIBLE FOR SUDDEN FREQUENCY DEVIATION AND GEOMAGNETIC FLUCTUATION

Data recorded by the Geostationary Operational Environmental Satellite s, frequency deviations derived from a CW-HF Doppler sounding system, and geomagnetic field strength variations obtained from ground-based m agnetometers were analyzed to study the ionospheric and geomagnetic so lar flare effects. A model of flare radiation was constructed from syn thetic flux intensities and satellite X ray observations, and correspo nding ionospheric frequency deviation and electron density at various altitudes were calculated. The evolution of solar EUV and X ray radiat ion and associated maximum values responsible fur frequency deviation and geomagnetic field strength fur various flux intensities of the exc ess solar radiation were studied in detail. It was found that during a solar flare, not only the magnitude of solar radiation, but also the rate of its change dramatically affects the maximum ionospheric freque ncy deviation. However, the results confirmed that only the intensity of solar radiation determines the magnitude of geomagnetic field stren gth.