The Heaviside layer,[1][2] sometimes called the Kennelly–Heaviside layer,[3][4] named after Arthur E. Kennelly and Oliver Heaviside, is a layer of ionisedgas occurring roughly between 90km and 150 km (56 and 93 mi) above the ground — one of several layers in the Earth's ionosphere. It is also known as the E region. It reflects medium-frequencyradio waves. Because of this reflective layer, radio waves radiated into the sky can return to Earth beyond the horizon. This "skywave" or "skip" propagation technique has been used since the 1920s for radio communication at long distances, up to transcontinental distances.
Layers of the ionosphere. The Kennelly–Heaviside layer is the E region
Propagation is affected by the time of day. During the daytime the solar wind presses this layer closer to the Earth, thereby limiting how far it can reflect radio waves. Conversely, on the night (lee) side of the Earth, the solar wind drags the ionosphere further away, thereby greatly increasing the range which radio waves can travel by reflection. The extent of the effect is further influenced by the season, and the amount of sunspot activity.
Existence of a reflective layer was predicted in 1902 independently and almost simultaneously by the American electrical engineer Arthur Edwin Kennelly (1861–1939)[5] and the British polymath Oliver Heaviside (1850–1925), as an explanation for the propagation of radio waves beyond the horizon observed by Guglielmo Marconi in 1901. However, it was not until 1924 that its existence was shown by British scientist Edward V. Appleton,[6] for which he received the 1947 Nobel Prize in Physics.[7]
Physicists resisted the idea of the reflecting layer for one very good reason; it would require total internal reflection, which in turn would require that the speed of light in the ionosphere would be greater than in the atmosphere below it. Since the latter speed is essentially the same as the speed of light in vacuum (c), scientists were unwilling to believe the speed in the ionosphere could be higher. Nevertheless, Marconi had received signals in Newfoundland that were broadcast in England, so clearly there must be some mechanism allowing the transmission to reach that far. The paradox was resolved by the discovery that there were two velocities of light, the phase velocity and the group velocity. The phase velocity can in fact be greater than c, but the group velocity, being capable of transmitting information, cannot, by special relativity, be greater than c. The phase velocity for radio waves in the ionosphere is indeed greater than c, and that makes total internal reflection possible, and so the ionosphere can reflect radio waves. The geometric mean of the phase velocity and the group velocity cannot exceed c, so when the phase velocity goes above c, the group velocity must go below it.
In 1925, Americans Gregory Breit and Merle A. Tuve first mapped the Heaviside layer's variations in altitude. The ITU standard model of absorption and reflection of radio waves by the Heaviside Layer was developed by the British Ionospheric physicist Louis Muggleton[8] in the 1970s.
Etymologyedit
Around 1910, William Eccles proposed the name "Heaviside Layer" for the radio-wave reflecting layer in the upper atmosphere,[1] and the name has subsequently been widely adopted.[2] The name Kennelly–Heaviside layer was proposed in 1925 to give credit to the work of Kennelly,[3][5] which predated the proposal by Heaviside by several months.
^ abGriffiths, Hugh (15 November 2018). "Oliver Heaviside and the Heaviside layer", Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences,376: No. 2134. https://doi.org/10.1098/rsta.2017.0459. Retrieved 14 June 2019.
^ abMarchant, E. W. (Dec. 1916). "The Heaviside layer", Proceedings of the Institute of Radio Engineers, 4, No. 6, pp. 511–520.
^ abMcAdie, Alexander (22 May 1925) "The Kennelly-Heaviside Layer", Science,61, No 1586, pp. 540 DOI: 10.1126/science.61.1586.540
^Martyn, D. F. (1934). "Atmospheric Pressure and the Ionisation of the Kennelly-Heaviside Layer". Nature. 133 (3356): 294. Bibcode:1934Natur.133R.294M. doi:10.1038/133294b0. ISSN 0028-0836. S2CID 684206.
^ abRussell, A. (24 October 1925). "The “Kennelly-Heaviside” Layer", Nature116, p. 609. doi:10.1038/116609c0
^Appleton, Edward V., and Barnett, M. A. F. (1 December 1925). "On some direct evidence for downward atmospheric reflection of electric rays", Proceedings of the Royal Society of London, Series A, Containing Papers of a Mathematical and Physical Character,109.752 pp. 621–641.
^"Nobel Prizes for 1947: Sir Edward Appleton, G.B.E., K.C.B., F.R.S.", Nature, 160, pp. 703–704 (22 November 1947) doi:10.1038/160703c0
^L.M. Muggleton (1975). "A method of predicting foE at any time and place". ITU Telecommunication Journal. 42: 413–418. Bibcode:1975ITUTJ..42..413M.
January 01, 1970
kennelly, heaviside, layer, this, article, needs, additional, citations, verification, please, help, improve, this, article, adding, citations, reliable, sources, unsourced, material, challenged, removed, find, sources, news, newspapers, books, scholar, jstor,. This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Kennelly Heaviside layer news newspapers books scholar JSTOR September 2015 Learn how and when to remove this template message The Heaviside layer 1 2 sometimes called the Kennelly Heaviside layer 3 4 named after Arthur E Kennelly and Oliver Heaviside is a layer of ionised gas occurring roughly between 90km and 150 km 56 and 93 mi above the ground one of several layers in the Earth s ionosphere It is also known as the E region It reflects medium frequency radio waves Because of this reflective layer radio waves radiated into the sky can return to Earth beyond the horizon This skywave or skip propagation technique has been used since the 1920s for radio communication at long distances up to transcontinental distances Layers of the ionosphere The Kennelly Heaviside layer is the E region Propagation is affected by the time of day During the daytime the solar wind presses this layer closer to the Earth thereby limiting how far it can reflect radio waves Conversely on the night lee side of the Earth the solar wind drags the ionosphere further away thereby greatly increasing the range which radio waves can travel by reflection The extent of the effect is further influenced by the season and the amount of sunspot activity Contents 1 History 2 Etymology 3 See also 4 ReferencesHistory editExistence of a reflective layer was predicted in 1902 independently and almost simultaneously by the American electrical engineer Arthur Edwin Kennelly 1861 1939 5 and the British polymath Oliver Heaviside 1850 1925 as an explanation for the propagation of radio waves beyond the horizon observed by Guglielmo Marconi in 1901 However it was not until 1924 that its existence was shown by British scientist Edward V Appleton 6 for which he received the 1947 Nobel Prize in Physics 7 Physicists resisted the idea of the reflecting layer for one very good reason it would require total internal reflection which in turn would require that the speed of light in the ionosphere would be greater than in the atmosphere below it Since the latter speed is essentially the same as the speed of light in vacuum c scientists were unwilling to believe the speed in the ionosphere could be higher Nevertheless Marconi had received signals in Newfoundland that were broadcast in England so clearly there must be some mechanism allowing the transmission to reach that far The paradox was resolved by the discovery that there were two velocities of light the phase velocity and the group velocity The phase velocity can in fact be greater than c but the group velocity being capable of transmitting information cannot by special relativity be greater than c The phase velocity for radio waves in the ionosphere is indeed greater than c and that makes total internal reflection possible and so the ionosphere can reflect radio waves The geometric mean of the phase velocity and the group velocity cannot exceed c so when the phase velocity goes above c the group velocity must go below it In 1925 Americans Gregory Breit and Merle A Tuve first mapped the Heaviside layer s variations in altitude The ITU standard model of absorption and reflection of radio waves by the Heaviside Layer was developed by the British Ionospheric physicist Louis Muggleton 8 in the 1970s Etymology editAround 1910 William Eccles proposed the name Heaviside Layer for the radio wave reflecting layer in the upper atmosphere 1 and the name has subsequently been widely adopted 2 The name Kennelly Heaviside layer was proposed in 1925 to give credit to the work of Kennelly 3 5 which predated the proposal by Heaviside by several months See also editVan Allen BeltReferences edit a b Griffiths Hugh 15 November 2018 Oliver Heaviside and the Heaviside layer Philosophical Transactions of the Royal Society A Mathematical Physical and Engineering Sciences 376 No 2134 https doi org 10 1098 rsta 2017 0459 Retrieved 14 June 2019 a b Marchant E W Dec 1916 The Heaviside layer Proceedings of the Institute of Radio Engineers 4 No 6 pp 511 520 a b McAdie Alexander 22 May 1925 The Kennelly Heaviside Layer Science 61 No 1586 pp 540 DOI 10 1126 science 61 1586 540 Martyn D F 1934 Atmospheric Pressure and the Ionisation of the Kennelly Heaviside Layer Nature 133 3356 294 Bibcode 1934Natur 133R 294M doi 10 1038 133294b0 ISSN 0028 0836 S2CID 684206 a b Russell A 24 October 1925 The Kennelly Heaviside Layer Nature 116 p 609 doi 10 1038 116609c0 Appleton Edward V and Barnett M A F 1 December 1925 On some direct evidence for downward atmospheric reflection of electric rays Proceedings of the Royal Society of London Series A Containing Papers of a Mathematical and Physical Character 109 752 pp 621 641 Nobel Prizes for 1947 Sir Edward Appleton G B E K C B F R S Nature 160 pp 703 704 22 November 1947 doi 10 1038 160703c0 L M Muggleton 1975 A method of predicting foE at any time and place ITU Telecommunication Journal 42 413 418 Bibcode 1975ITUTJ 42 413M Retrieved from https en wikipedia org w index php title Kennelly Heaviside layer amp oldid 1170141226, wikipedia, wiki, book, books, library,
