High frequency waves in this band can be reflected back to Earth by the ionosphere layer in the atmosphere – a method known as "skip" or "skywave" propagation – these frequencies are suitable for long-distance communication across intercontinental distances. The band is used by international shortwave broadcasting stations (2.31–25.82 MHz), aviation communication, government time stations, weather stations, amateur radio and citizens band services, among other uses. The dominant means of long distance communication in this band is skywave ("skip") propagation, in which radio waves directed at an angle into the sky refract back to Earth from layers of ionized atoms in the
Radio star and beam out coherent bursts of microwaves. The Sun, the nearest star to Earth, is known to emit radio waves, though it is virtually the only regular star that has been detected in the radio spectrum, because it is so close. It is not considered a radio star because it is not a strong radio source. Some studies have found that main-sequence stars may extremely rarely emit radio waves. A 2009 survey found a maximum of 112 candidate radio stars cross-matching the FIRST and NVSS surveys, but estimated that 108 ± 13 of the samples are from "contamination" from background