Kennelly–Heaviside layer Kennelly–Heaviside layer The Kennelly–Heaviside layer, named after Arthur E. Kennelly and Oliver Heaviside, also known as the E region or simply the Heaviside layer, is a layer of ionised gas occurring between roughly 90–150 km (56–93 mi) above the ground — one of several layers in the Earth's ionosphere. It reflects medium-frequency radio waves. Because of this reflective layer, radio waves radiated into the sky can return to Earth beyond the horizon. This "skywave" or "skip" propagation technique has been used since the 1920s for radio communication at long distances, up to transcontinental distances. Propagation is affected by time of
Atmospheric wave Atmospheric wave An atmospheric wave is a periodic disturbance in the fields of atmospheric variables (like surface pressure or geopotential height, temperature, or wind velocity) which may either propagate ("traveling wave") or not ("standing wave"). Atmospheric waves range in spatial and temporal scale from large-scale planetary waves (Rossby waves) to minute sound waves. Atmospheric waves with periods which are harmonics of 1 solar day (e.g. 24 hours, 12 hours, 8 hours... etc.) are known as atmospheric tides. The mechanism for the forcing of the wave, for example the generation of the initial or prolonged disturbance in the atmospheric variables, can