Artificial periodic inhomogeneities in the lower part of the D region at sunset and sunrise

The amplitude and relaxation time variations in artificial periodic inhomogeneities (API) in the lower part of the D region in the sunrise and sunset period are discussed. The analysis is carried out on the basis of the ionospheric model with two negative ions. The API diagnostic is performed by the backward scattering method of pulsed radiowaves at the 5.75 MHz frequency coinciding with the exciting transmitter frequency. A satisfactory agreement between the experimental results and calculation data is attained