Radio Emission of Rydberg Atoms in the Upper Atmosphere Modified by High-Power HF Radio Waves

We report on the results of studying the radio emission of the Rydberg states of atoms and molecules in the Earth’s upper atmosphere at ionospheric altitudes when the ionosphere is modified by high-power HF radio waves radiated by the Sura heating facility. Radio emission from the upper atmosphere, caused by the emission of highly excited Rydberg atoms and molecules with the principal quantum number n = 163–169 and n = 225 (decimeter wavelength range) and two spectral features that coincide with the frequencies of transitions between Rydberg states m = 169 → n = 168 with the transition frequency νn = 1375.35 MHz and m = 166 → n = 165 with νn = 1451.5 MHz were detected. Characteristic altitudes of the Rydberg radiation generation region were 150–250 km. The radio emission intensity corresponds to 10–45 K, which is comparable with the intensity of the radio emission generated during solar flares.