Adaptation of model parameters of VLF radio signals phase variations on the Novosibirsk - Yakutsk propagation path

Phase variations and sudden phase anomalies (SPA) VLF signals registered in Yakutsk from Novosibirsk radio station (14.9 kHz) for summer and winter daytime propagation conditions are considered. The threshold SPA sensitivity by Xrays flux P depends on the season weakly. SPA magnitude at fixed solar zenith angle X and X-ray flux P from summer to winter on the Novosibirsk - Yakutsk path is increased, SPA dependence on averaged along the propagation path of the cosine solar zenith angle is sharper in summer. X-ray flux is estimated according to the phase variations of the Novosibirsk radio signals. A satisfactory agreement with the simulated flux data from the satellite has been obtained booth in SPA, and unperturbed daytime conditions.