Auroral And Meteor-Scatter Propagation:

In the presence of strange solar activity, the aurora frequently reflects radio waves at certain frequencies. This is termed as auroral propagation. The aurorae take place in the ionosphere at altitudes of 25 km (i.e., 40 mi) to 400 km (i.e., 250 mi) above the surface. Hypothetically, auroral propagation is possible, whenever the aurorae are active, among any two points on the Earth's surface from which the similar portion of the aurora lies on a line of sight. The auroral propagation seldom takes place if either the transmitter or the receiver is at latitude less than 35 degrees north or south of the equator. The auroral propagation can occur at frequencies well above 30 MHz and frequently is accompanied by deterioration in ionospheric propagation through the E and F layers.

Whenever a meteor from space comes in the upper portion of the atmosphere, an ionized trail is generated since of the heat of friction. Such an ionized area reflects EM energy at some wavelengths. This phenomenon, termed as meteor-scatter propagation, can outcome in over-the-horizon radio communication or reception.

A meteor generates a trail which persists for a few tenths of a second up to numerous seconds depending on the size of the meteor, its speed, and the angle at which it comes in the atmosphere. This quantity of time is not enough for the transmission of very much information, though during a meteor shower, ionization can be almost constant. Meteor scatter propagation has been examined at frequencies considerably above 30 MHz and takes place over distances ranging from just beyond the horizon up to around 2,000 km (i.e., 1,200 mi) based on the altitude of the ionized trail and on the associative positions of the trail, the transmitting station, and the receiving station.