Effect of neutral particle density in the upper atmosphere on the generation of artificial magnetic pulsations in the Pc1 range

A series of experiments on modification of the ionosphere by a powerful ground HF transmitter was performed using the EISCAT heating facility in order to generate artificial magnetic pulsations in the frequency range 0.1–3 Hz. In several cases, the ionospheric electric field and the electron density vertical profile were measured with the EISCAT incoherent scatter radar. The measurement of the background values of the ionospheric parameters made it possible to verify the numerical model for generating artificial emissions. The calculated amplitudes of magnetic pulsations correspond to the values measured on the Earth’s surface. However, the model cannot explain the sporadic nature of artificial signals, which indicates that this model is incomplete. Disturbances of the neutral particle density in the upper atmosphere are one of the possible causes explaining a difference between the calculations and the experimental values. The numerical simulation indicated that the amplitude variations caused by such disturbances can be 20%. For artificial emissions whose intensity is comparable with the intensity of artificial noise, variations in the neutral components can result in the disappearance of an artificial signal on the spectrogram.