THE CALCULATION OF LOWER IONOSPHERIC TEC ENHANCEMENT DURING INITIAL FLARE BURST USING HF DOPPLER RECORDS

By analyzing the change of electron density in different ionospheric regionsduring flare bursts, a new method is introduced, by which the TEC enhancement inthe lower ionosphere during the initial phase of a flare burst can be calculated using HF Doppler records. Some TEC enhancements caused by flare bursts from Marchto June in 1990 are calculated using this method. The results of TECenhancementare compared with the maximum fluxes of the soft X--ray of the corresponding flares.The correlation between the calculated TEC enhancement and maximum fluxes ofthe soft X-ray radiation of solar flares are fairly good in general, except very intenseflares.