Empirical models of Ne(h) profiles in the F2 region for the territory of Bulgaria

F2 Ne(h) profiles are investigated on the basis of data of ionospheric vertical sounding from the Sofia station during the nocturnal hours of the period August 28-September 2, 1986. During this period short-term precursors of the earthquake in Vrancea on August 31, 1986 were observed. Empirical models of the F-region are constructed which make it possible to accurately determine seismic ionospheric effects for the region of Bulgaria and to trace the deformation in Ne(h) profiles of the F-region under the above conditions, especially under conditions when short-term ionospheric precursors are present.