Atmospheric Electricity

Atmospheric electricity is the regular diurnal variations of the Earth's atmospheric electromagnetic network or, more broadly, any planet's electrical system in its layer of gases. The Earth's surface, the atmosphere and the ionosphere, together are known as the global atmospheric electrical circuit. Atmospheric electricity is a multidisciplinary topic.

There is always free electricity in the air and in the clouds, which acts by induction on the earth and electromagnetic devices. Experiments have shown that there is always free electricity in the atmosphere, which is sometimes negative and sometimes positive, but most generally positive, and the intensity of this free electricity is greater in the middle of the day than at morning or night and is greater in winter than in summer. In fine weather, the potential increases with altitude at about 30 volts per foot (100 V/m).

The atmospheric medium, by which we are surrounded, contains not only combined electricity, like every other form of matter, but also a considerable quantity in a free and uncombined state; sometimes of one kind, sometimes of the other; but as a general rule it is always of an opposite kind to that of the Earth. Different layers, or strata, of the atmosphere, located at only small distances from each other, are frequently found to be in different electric states. The phenomena of atmospheric electricity are of three kinds. There are the electrical phenomena of thunderstorms and there are the phenomena of continual electrification in the air. The phenomena of the polar auroras constitute a third branch of the subject.

Most authorities are agreed, however, that whatever may be the origin of free electricity in the atmosphere, the electricity of enormous voltages that disrupts the air and produces the phenomena of lightning is due to the condensation of the watery vapor forming the clouds; each minute drop, as it moves through the air, collects upon its surface a certain amount of free electricity. Then, as these tiny drops coalesce into larger drops, with a corresponding decrease in the relative surface exposed, the electric potential rises until it overcomes the resisting power of the air. This remark will be more clearly understood when it is considered that, with a given charge of electricity, an object's potential rises as the electrical capacity of the object holding the charge is decreased, which is the case when the minute drops coalesce into larger drops. The similarity of lightning to the electricity developed by an electrical machine was demonstrated by Franklin in his memorable kite experiments.