The Northern Lights
The aurora borealis (or aurora austalis in southern hemisphere) occurs after solar flares cause the E layer in the atmosphere to become ionised. The particles which cause the ionisation are constantly moving around. Vhf radio signals can be reflected from this area, because it not stable the reflected signals are affected by doppler shift causing the received audio to have a rasping sound.
A 11 second clip of an auroral QSO
A 8 second clip of an auroral QSO
