What layer of the atmosphere is reflected by radio waves?

Radio waves are primarily reflected by the ionosphere, which is a region of the Earth's atmosphere located roughly between 30 miles (48 kilometers) and 600 miles (965 kilometers) above the surface. The ionosphere contains a high concentration of ionized particles, which can reflect certain frequencies of radio waves, allowing for long-distance communication. This reflection occurs mainly during the daytime when solar radiation ionizes the atmospheric gases.