Exotic modes of EM propagation

Radio waves can bounce off aurora (northern and southern lights). This is auroral propagation, and it occurs at frequencies from around 15 to 250 MHz. It can occur between stations separated by up to around 2000 miles.Meteors entering upper atmosphere produce ionized trails which persist for several seconds up to about a minute; these ions reflect the EM waves and create meteor-scatter propagation. This mode allows the communication for hundreds of miles at the frequencies from 20 to 150 MHz.

The moon, like earth, reflects EM fields. This makes it probable to communicate by means of earth-moon-earth  (EME),  called as moonbounce. The high-powered transmitters, sophisticated antenna systems, and the sensitive receivers are required for EME. Most EME is done by the radio hams at frequencies from around 50 MHz to over 2 GHz.