What is "atmospheric electricity"

Electricity \E`lec*tric"i*ty\ ([=e]`l[e^]k*tr[i^]s"[i^]*t[y^]), n.; pl. Electricities ([=e]`l[e^]k*tr[i^]s"[i^]*t[i^]z).

1. (Physics) a property of certain of the fundamental particles of which matter is composed, called also electric charge, and being of two types, designated positive and negative; the property of electric charge on a particle or physical body creates a force field which affects other particles or bodies possessing electric charge; positive charges create a repulsive force between them, and negative charges also create a repulsive force. A positively charged body and a negatively charged body will create an attractive force between them. The unit of electrical charge is the coulomb, and the intensity of the force field at any point is measured in volts.

2. any of several phenomena associated with the accumulation or movement of electrically charged particles within material bodies, classified as static electricity and electric current. Static electricity is often observed in everyday life, when it causes certain materials to cling together; when sufficient static charge is accumulated, an electric current may pass through the air between two charged bodies, and is observed as a visible spark; when the spark passes from a human body to another object it may be felt as a mild to strong painful sensation. Electricity in the form of electric current is put to many practical uses in electrical and electronic devices. Lightning is also known to be a form of electric current passing between clouds and the ground, or between two clouds. Electric currents may produce heat, light, concussion, and often chemical changes when passed between objects or through any imperfectly conducting substance or space. Accumulation of electrical charge or generation of a voltage differnce between two parts of a complex object may be caused by any of a variety of disturbances of molecular equilibrium, whether from a chemical, physical, or mechanical, cause. Electric current in metals and most other solid coductors is carried by the movement of electrons from one part of the metal to another. In ionic solutions and in semiconductors, other types of movement of charged particles may be responsible for the observed electrical current. Note: Electricity is manifested under following different forms:

   1. Statical electricity, called also

      Frictional electricity or Common electricity, electricity in the condition of a stationary charge, in which the disturbance is produced by friction, as of glass, amber, etc., or by induction.

   2. Dynamical electricity, called also

      Voltaic electricity, electricity in motion, or as a current produced by chemical decomposition, as by means of a voltaic battery, or by mechanical action, as by dynamo-electric machines.

   3. Thermoelectricity, in which the disturbing cause is heat (attended possibly with some chemical action). It is developed by uniting two pieces of unlike metals in a bar, and then heating the bar unequally.

   4. Atmospheric electricity, any condition of electrical disturbance in the atmosphere or clouds, due to some or all of the above mentioned causes.

   5. Magnetic electricity, electricity developed by the action of magnets.

   6. Positive electricity, the electricity that appears at the positive pole or anode of a battery, or that is produced by friction of glass; -- called also vitreous electricity.

   7. Negative electricity, the electricity that appears at the negative pole or cathode, or is produced by the friction of resinous substance; -- called also resinous electricity.

   8. Organic electricity, that which is developed in organic structures, either animal or vegetable, the phrase animal electricity being much more common.

3. The science which studies the phenomena and laws of electricity; electrical science.

4. Fig.: excitement, anticipation, or emotional tension, usually caused by the occurrence or expectation of something unusual or important.

n. electrical discharges in the atmosphere

Atmospheric electricity is the pattern of electrical charges in the Earth's atmosphere (or less commonly, that of another planet). The normal movement of electric charges among the Earth's surface, the various layers of the atmosphere, and especially the ionosphere, taken together, are known as the global atmospheric electrical circuit. Much of the reasoning required to explain these currents lies within the field of electrostatics, but also requires understanding of other disciplines within Earth science.

Eliminating, for the moment, consideration of the extremely dense charge populations that exist in the upper reaches of the atmosphere, a region called the ionosphere, filled with hot, dense, plasma gas whose ions give the ionosphere its name, we note that there is always some amount of unbound positive and negative, but net positive, electric charge in the atmosphere closest to the surface of the negatively charged Earth on a 'fine day'. When days are not so 'fine', the net unbound charge that exists in the clouds of thunderstorms can be exceedingly negative.

The 'fine day' net positive charge sets up an electric field between the negative Earth and the net positive charge in the air, and this electric field stores electrical energy. The positive charge acts by induction on the earth and electromagnetic devices.

Experiments have shown that the intensity of this electric field is greater in the middle of the day than at morning or night and is also greater in winter than in summer. In 'fine weather', the potential, aka 'voltage', increases with altitude at about 30 volts per foot (100 V/m), when climbing against the gradient of the electric field. This electric field gradient continues up into the atmosphere to a point where the voltage reaches its maximum, in the neighborhood of 300,000 volts. This occurs at approximately 30–50 km above the Earth's surface. From that point in the atmosphere up to its outer limit, nearly 1,000 km, the electric field gradient produced in the lower atmosphere either ceases or has reversed.

Global daily cycles, with a minimum around 03 UT and peaking roughly 16 hours later, were researched by the Carnegie Institution of Washington in the 20th century. This Carnegie curve variation has been described as "the fundamental electrical heartbeat of the planet".

The phenomena characterizing atmospheric electricity are of at least three kinds. There are thunderstorms, which create lightning bolts that 'instantaneously' discharge huge amounts of atmospheric charge to ground in a rapid release of energy stored in the electric field that built up to a particularly extreme degree in the storm clouds. There is a related phenomenon of continual electrification (re-charging) of the air in the lower atmosphere. A third phenomenon is that of the polar auroras.

Most authorities agree that whatever may be the origin of the net unbound positive charge in the atmosphere, the generation of enormous currents (flow of electrons, negative charges), that flow between clouds and ground during a lightning discharge, begins with condensation of water vapor within the clouds; each minute water droplet moving through the air collects upon its surface a certain amount of negative charge by collecting 'free' electrons. As these tiny drops coalesce into larger drops, and still larger drops, there is a corresponding decrease in the total exposed surface upon which the collected electronic charges can be carried, raising the negative voltage as droplets combine. This is because an object's potential rises as the electrical capacitance of the object holding the charge is decreased. The combined negative electric potential of all the coalescing water drops rises until it overcomes the breakdown voltage of the, usually non-conductive, air, and jumps to earth as a lightning bolt. The similarity of lightning to the discharge of accumulated electrons developed on an electrical machine was demonstrated by Franklin in his memorable kite experiments.