Global atmospheric electrical circuit Global atmospheric electrical circuit The global atmospheric electrical circuit is the course of continuous movement of atmospheric electricity between the ionosphere and the Earth. Through solar radiation, thunderstorms, and the fair-weather condition, the atmosphere is subject to a continual and substantial electrical current. Principally, thunderstorms throughout the world carry "negative" charges to the earth, which is then discharged gradually through the air in fair weather. This atmospheric circuit is central to the study of atmospheric physics and meteorology. It is used in the prediction of thunderstorms, and was central to the understanding of electricity. In the past it has been
Radio propagation degrade transmission. At lower frequencies in the MF, LF, and VLF bands, due to diffraction radio waves can bend over obstacles like hills, and travel beyond the horizon as surface waves which follow the contour of the Earth. These are called ground waves. AM broadcasting stations use ground waves to cover their listening areas. As the frequency gets lower, the attenuation with distance decreases, so very low frequency (VLF) and extremely low frequency (ELF) ground waves can be used to communicate worldwide. VLF and ELF waves can penetrate significant distances through water and earth, and these frequencies are used for