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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.〔Richard Spelman Culley, ''A Handbook of Practical Telegraphy''. Longmans 1885. (Page 104 )〕 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.〔Retrieved 9Jan. 2013. Posted by MIT graduate student Jason Goodman on Oct. 27, 2000 on the Mad Scientist Network at http://www.madsci.org/posts/archives/2000-10/972662284.Es.r.html〕 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〔R. Giles Harrison, The Carnegie Curve. Springer. http://link.springer.com/article/10.1007%2Fs10712-012-9210-2〕 variation has been described as "the fundamental electrical heartbeat of the planet".〔Atmospheric electricity affects cloud height - physicsworld.com http://physicsworld.com/cws/article/news/2013/mar/06/atmospheric-electricity-affects-cloud-height〕 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.〔Atmospheric charging is best observed when the weather is fair.〕 A third phenomenon is that of the polar auroras.〔Silvanus Phillips Thompson, ''(Elementary Lessons in Electricity and Magnetism )''. 1915.〕 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.〔 ==History== (詳細はsparks drawn from electrical machines and from Leyden jars suggested to the early experimenters, Hauksbee, Newton, Wall, Nollet, and Gray, that lightning and thunder were due to electric discharges.〔 In 1708, Dr. William Wall was one of the first to observe that spark discharges resembled miniature lightning, after observing the sparks from a charged piece of amber. In the middle of the 18th century, Benjamin Franklin's experiments showed that electrical phenomena of the atmosphere were not fundamentally different from those produced in the laboratory. By 1749, Franklin observed lightning to possess almost all the properties observable in electrical machines.〔 In July 1750, Franklin hypothesized that electricity could be taken from clouds via a tall metal aerial with a sharp point. Before Franklin could carry out his experiment, in 1752 Thomas-François Dalibard erected a iron rod at Marly-la-Ville, near Paris, drawing sparks from a passing cloud.〔 With ground-insulated aerials, an experimenter could bring a grounded lead with an insulated wax handle close to the aerial, and observe a spark discharge from the aerial to the grounding wire. In May 1752, Dalibard affirmed that Franklin's theory was correct. Franklin listed the following similarities between electricity and lightning: * producing light of a similar color; * rapid motion; * being conducted by metals, water and ice; * melting metals and igniting inflammable substances; * "sulfurous" smell (which is now known to be due to ozone); * magnetizing needles; * the similarity between St. Elmo's Fire and glow discharge. Around June 1752, Franklin reportedly performed his famous kite experiment. The kite experiment was repeated by Romas, who drew from a metallic string sparks long, and by Cavallo, who made many important observations on atmospheric electricity. L. G. Lemonnier (1752) also reproduced Franklin's experiment with an aerial, but substituted the ground wire with some dust particles (testing attraction). He went on to document the ''fair weather condition'', the clear-day electrification of the atmosphere, and the diurnal variation of the atmosphere's electricity. G. Beccaria (1775) confirmed Lemonnier's diurnal variation data and determined that the atmosphere's charge polarity was positive in fair weather. H. B. Saussure (1779) recorded data relating to a conductor's induced charge in the atmosphere. Saussure's instrument (which contained two small spheres suspended in parallel with two thin wires) was a precursor to the electrometer. Saussure found that the fair weather condition had an annual variation, and found that there was a variation with height, as well. In 1785, Coulomb discovered the electrical conductivity of air. His discovery was contrary to the prevailing thought at the time, that the atmospheric gases were insulators (which they are to some extent, or at least not very good conductors when not ionized). His research was, unfortunately, completely ignored. P. Erman (1804) theorized that the Earth was negatively charged. J. C. A. Peltier (1842) tested and confirmed Erman's idea. Lord Kelvin (1860s) proposed that atmospheric positive charges explained the ''fair weather condition'' and, later, recognized the existence of atmospheric electric fields. Over the course of the next century, using the ideas of Alessandro Volta and Francis Ronald,〔Sir Francis Ronald constructed an electric telegraph, 8 miles long, in 1816. See Nature, Volume 25 edited by Sir Norman Lockyer, (page 515 ).〕〔"(Ronalds, Sir Francis )" Oxford DNB〕〔He later willed and disposed his personal library to the Society of Telegraph Engineers.〕 several researchers contributed to the growing body of knowledge about atmospheric electrical phenomena. With the invention of the portable electrometer and Lord Kelvin's 19th century water-dropping condenser, a greater level of precision was introduced into observational results. Towards the end of the 19th century came the discovery by W. Linss (1887)〔Linss, Meteorol. Zeitschr. iv. p. 352, 1887; Etektrotechn. Zeitschr. i. 11, p. 506, 1890, 38th issue.〕〔''Ueber einige die Wolken-und Luftelectricitat betreffende Probleme'' (tr., ''Over the clouds and some relevant air electricity problems''). 17 pp. Contained in ''Meteorologische Zeitschrift. Herausgegeben Von Der ÖsterreichIschen Gesellschaft Für Meteorologie Und Der Deutschen MeteoroLogischen Gesellschaft''. Redigirt von Dr. J. Hann und Dr. W. Koppen. October–December 1887.〕〔Terrestrial magnetism, Volumes 3-4 edited by Louis Agricola Bauer. (Page 65 ).〕〔Conduction of electricity through gases By Sir Joseph John Thomson. (Page 3 ).〕 that even the most perfectly insulated conductors lose their charge, as Coulomb before him had found, and that this loss depended on atmospheric conditions. H. H. Hoffert (1888) identified individual lightning downward strokes using early cameras and would report this in "''Intermittent Lightning-Flashes''".〔Proceedings of the Physical Society: Volumes 9-10. Institute of Physics and the Physical Society, Physical Society (Great Britain), Physical Society of London, 1888. Intermittent Lightning-Flashes. By HH Hoffert. (Page 176 ).〕 J. Elster and H. F. Geitel, who also worked on thermionic emission, proposed a theory to explain thunderstorms' electrical structure (1885) and, later, discovered atmospheric radioactivity (1899).〔Alessandro De Angelisa, Atmospheric ionization and cosmic rays: studies and measurements before 1912. http://arxiv.org/pdf/1208.6527.pdf.〕 By then it had become clear that freely charged positive and negative ions were always present in the atmosphere, and that radiant emanations could be collected.〔〔William Ramsay. The Gases of the Atmosphere: The History of Their Discovery. (Page 300 )〕 F. Pockels (1897) estimated lightning current intensity by analyzing lightning flashes in basalt (c. 1900)〔Vladimir A. Rakov, Martin A. Uman. Lightning: Physics and Effects. Page 3.〕 and studying the left-over magnetic fields.〔Basalt, being a ferromagnetic mineral, becomes magnetically polarised when exposed to a large external field such as those generated in a lightning strike. See ''Anomalous Remanent Magnetization of Basalt'' pubs.usgs.gov/bul/1083e/report.pdf for more.〕 Using a ''Peltier electrometer'', Luigi Palmieri researched atmospheric electricity.〔Nature - Volume 40 - (Page 209 )〕 Nikola Tesla and Hermann Plauson investigated the production of energy and power via atmospheric electricity.〔Nikola Tesla, The Problem of Increasing Human Energy.〕〔The Engineering Index. American Society of Mechanical Engineers, 1921.( Page 230 )〕 Tesla also proposed to use the atmospheric electrical circuit to transceive wireless energy over large distances.〔Thomas Valone (Harnessing the wheelwork of nature: Tesla's science of energy )〕〔See his Wardenclyffe Tower and Magnifying Transmitter)〕 The Polish Polar Station, Hornsund, has researched the magnitude of the Earth's electric field and recorded its vertical component.〔Polish Polar Station Hornsund, Spitsbergen http://hornsund.igf.edu.pl/index_en.php〕 Discoveries about the electrification of the atmosphere via sensitive electrical instruments and ideas on how the Earth’s negative charge is maintained were developed mainly in the 20th century.〔(Encyclopedia of Geomagnetism and Paleomagnetism ) - Page 359〕 Whilst a certain amount of observational work has been done in the branches of atmospheric electricity, the science has not developed to a considerable extent.〔Atmospheric electricity Lieut. C. D. Stewart R.E., B.Sc., F.R.MetSoc. Article first published online: AUG 15, 2007 DOI: 10.1002/qj.49704318406〕 Up to the contemporary day, apparatus which extract industrial energy from atmospheric electricity have not been built and maintained. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「atmospheric electricity」の詳細全文を読む スポンサード リンク
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