Analysis of the effect of cosmic noise absorption increase on propagation of auroral hiss to the ground

We analyze the effect of changes in the cosmic radio noise absorption in the lower ionosphere on propagation of the auroral hiss to the ground, using observational data from the Lovozero and Tumanny observatories. Three bursts of auroral hiss have been examined whose termination is accompanied by an increase in riometric absorption up to 0.6–2.2 dB. Modeling their propagation from the magnetosphere to the ground under conditions of a perturbed electron density profile, caused by precipitation of energetic electrons, shows that even a small absorption of 0.6 dB in the ionosphere causes the auroral hiss to weaken by 45–50 dB relative to its power at an altitude of 800 km. Calculations show that with such absorption the auroral hiss power near the ground is comparable to the level of natural noise of the Earth — ionosphere waveguide, and with riometric absorption of 2.2 dB a complete termination of the auroral hiss on the ground can be expected.