Whistler (Radio)

A Whistler is a low frequency electromagnetic signal that can be generated for example by a thunderstorm. The frequencies of Whistlers are between 1 and 30 kHz, usually with a maximum 3-5 kHz. Thus, they are frequenzlich in the audible range of humans and can be converted to a suitable receiver directly into acoustic signals.

They result from lightning strikes, wherein the pulse of the earth moves away and returns along the magnetic field lines to the ground. Due to the lower propagation velocity (dispersion) of the lower frequencies in the plasma of the ionosphere and magnetosphere, they are perceived as descending tone that can last for several seconds. Whistlers are divided into Pure Note Whistlers, Diffuse, 2 -hop and Echo Train.

Whistler were also received from Jupiter, which proves the local existence of thunderstorms.

Designations

The propagation of a signal in the Earth- ionosphere waveguide is referred to as sferics. If the signal is originated in the ionosphere and can propagate through the magnetosphere, it comes to a diving spread, when it is at the opposite sides of the planet reflected back and forth until it is completely attenuated. In order to clarify which part of this hopping pattern the signal is located, a number is assigned to it. On its first upward path, it is called a 0 . After passing through the magnetic equator, it is considered 1 - respectively. The or - sign indicates the upward or downward propagation. The number represents the current mid- jump number. The re- reflected signal is then referred as 1 , until it again passes through the geomagnetic equator; then it's 2 -, etc.