Abnormal Radio Propagation

Like many others, J. Raymond of Fairbanks has noted the vagaries of AM radio reception in Alaska and has asked if reception is better in Alaska than elsewhere. He rightly notes that the peculiarities of broadcast band radio in Alaska are related to the aurora.

Those same incoming charged particles (mainly electrons) that stream down along the direction of the earth's magnetic field over central and northern Alaska to create the visible aurora also modify the ionosphere. Irregularly shaped regions of enhanced electron density associated with aurora in the ionosphere, altitude 100 km (60 mi.) and above, both absorb and reflect radio waves.

For the most part, the auroral particles interfere with ionospheric radio propagation, making it less reliable in Alaska and other polar regions than at lower latitudes. But sometimes the auroral effects lead to weird and wondrous propagation paths. This is why listeners in Chalkyitsik sometimes receive AM radio from Hungary, China, or South America. It explains why Fairbanks cab drivers sometimes receive instructions from dispatchers in Miami or New Jersey. Such radio waves may bounce several times between the ionosphere and the earth's surface before reaching the destination where heard. The radio waves used to send television and telephone messages via satellite are of much higher frequency. These travel only line-of-sight paths from antenna to antenna and are little deviated by the ionosphere.