Impact of the auroral ionosphere on HF radio propagation

Quality of the HF communications at the high latitudes depends on a state of the ionosphere and radio wave propagation conditions. Absorption (auroral and polar cap) of HF signal power, the anomalous ionization in the ionospheric F-region (F2S) at night-hours of winter and equinox, significant negative disturbances in the F2-layer at day-time of all seasons, effect of the non-great-circle propagation, formation of some sporadic Es-layers of different types, increased diffusion of signals reflected from the ionosphere and signal distortions caused by rapid and deep fadings often take place here. The aims of the present study are (1) to determine the extent to which the quality of transmitted information through the real HF links located inside the auroral zone (ΦL = 64 66°) is affected by the MIT, the sporadic Es-layers, the F2S regions and the auroral absorption; (2) to reveal how to select the optimal operating frequencies correctly on these links for increasing the communication quality under the most difficult conditions of signal broadcasting. The mentioned tasks will be considered basically on the materials of long complex experiments.