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Kennelly–Heaviside Layer
The Heaviside layer, sometimes called the Kennelly–Heaviside layer, 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. 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 exten ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ionosphere Layers En
The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays an important role in atmospheric electricity and forms the inner edge of the magnetosphere. It has practical importance because, among other functions, it influences radio propagation to distant places on Earth. History of discovery As early as 1839, the German mathematician and physicist Carl Friedrich Gauss postulated that an electrically conducting region of the atmosphere could account for observed variations of Earth's magnetic field. Sixty years later, Guglielmo Marconi received the first trans-Atlantic radio signal on December 12, 1901, in St. John's, Newfoundland (now in Canada) using a kite-supported antenna for reception. The transmitting station in Poldhu, Cornwall, used a spark-gap transmitter to produce a signal with a fre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Edward V
Edward V (2 November 1470 – mid-1483)R. F. Walker, "Princes in the Tower", in S. H. Steinberg et al, ''A New Dictionary of British History'', St. Martin's Press, New York, 1963, p. 286. was ''de jure'' King of England and Lord of Ireland from 9 April to 25 June 1483. He succeeded his father, Edward IV, upon the latter's death. Edward V was never crowned, and his brief reign was dominated by the influence of his uncle and Lord Protector, the Duke of Gloucester, who deposed him to reign as King Richard III Richard III (2 October 145222 August 1485) was King of England and Lord of Ireland from 26 June 1483 until his death in 1485. He was the last king of the House of York and the last of the Plantagenet dynasty. His defeat and death at the Battl ...; this was confirmed by the Act of Parliament, Act entitled ''Titulus Regius'', which denounced any further claims through his father's heirs. Edward V and his younger brother Richard of Shrewsbury, Duke of York, were the Prin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ionosphere
The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays an important role in atmospheric electricity and forms the inner edge of the magnetosphere. It has practical importance because, among other functions, it influences radio propagation to distant places on Earth. History of discovery As early as 1839, the German mathematician and physicist Carl Friedrich Gauss postulated that an electrically conducting region of the atmosphere could account for observed variations of Earth's magnetic field. Sixty years later, Guglielmo Marconi received the first trans-Atlantic radio signal on December 12, 1901, in St. John's, Newfoundland (now in Canada) using a kite-supported antenna for reception. The transmitting station in Poldhu, Cornwall, used a spark-gap transmitter to produce a signal with a freq ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
William Eccles (physicist)
William Henry Eccles FRS (23 August 1875 – 29 April 1966) was a British physicist and a pioneer in the development of radio communication. He was born in Barrow-in-Furness, Lancashire, England. Following graduation from the Royal College of Science, London, in 1898, he became an assistant to Guglielmo Marconi, the Italian radio entrepreneur. In 1901 he received his doctorate from the Royal College of Science. Eccles was an advocate of Oliver Heaviside's theory that a conducting layer of the upper atmosphere could reflect radio waves around the curvature of the Earth, thus enabling their transmission over long distances. Originally known as the Kennelly–Heaviside layer, this region of the Earth's atmosphere became known as the ionosphere. In 1912 Eccles suggested that solar radiation was responsible for the observed differences in radio wave propagation during the day and night. He carried out experiments into atmospheric disturbances of radio waves and used wave detecto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Louis Miles Muggleton
Louis Miles Muggleton, FIET (8 July 1922 – 5 April 2015) was a South African-born British Ionospheric Physicist and Electrical Engineer. Building on the work of Sir Edward Appleton in 1975 Muggleton's seminal work provided the international standard ITU model of radio wave absorption and reflection of the Heaviside layer (or E-layer) of the Ionosphere. This model was based on jointly published work with Stamatis Kouris from the early 1970s. Biography Louis Muggleton was born in Sterkstroom, South Africa, the son of Oscar Muggleton and Ethel Helen Eliza Verran. Educated at Umtali High School in Southern Rhodesia, in 1940 he was awarded a Beit Engineering Scholarship to the University of Cape Town where he graduated with a first class BSc degree in 1948. This was followed by a PhD in Antenna Design in 1960. During the Second World War he joined the British Army, travelled to England, and transferred to the Royal Corps of Signals. Within a year he was promoted to lieuten ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Merle A , a commune in southern France
{{disambiguation ...
Merle may refer to: People *Merle (given name), a given name used by both men and women *Merle (surname), a surname of French origin Others *Merle (dog coat), a pattern in dogs’ coats *Merle (grape), another name for the wine grape Merlot *Akaflieg München Mü17 Merle, a German glider originally built in 1938 for the 1940 Olympics gliding competition * MS ''Phocine'', a ferry formerly named MS ''Merle'' *Merle's Tune, a hymn tune composed by Hal Hopson in 1983 *A Crusader fort near Tantura on the coast of Israel *The French name for the common blackbird See also *Merl (other) *Merles Merles (; oc, Mèrles) is a commune in the Tarn-et-Garonne department in the Occitanie region in southern France. See also *Communes of the Tarn-et-Garonne department The following is a list of the 195 communes of the Tarn-et-Garonne depar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gregory Breit
Gregory Breit (russian: Григорий Альфредович Брейт-Шнайдер, ''Grigory Alfredovich Breit-Shneider''; July 14, 1899, Mykolaiv, Kherson Governorate – September 13, 1981, Salem, Oregon) was a Russian-born Jewish American physicist and professor at New York University (1929–1934), University of Wisconsin–Madison (1934–1947), Yale University (1947–1968), and University at Buffalo (1968–1973). In 1921, he was Paul Ehrenfest's assistant in Leiden University. Biography After completing his Ph.D. at age 22, he was from 1923 to 1924 an assistant professor at the University of Minnesota. In 1925, while at the Carnegie Institution of Washington, Breit joined with Merle Tuve in using a pulsed radio transmitter to determine the height of the ionosphere, a technique important later in radar development. Together with Eugene Wigner, Breit gave a description of particle resonant states with the relativistic Breit–Wigner distribution in 1929, and wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Special Relativity
In physics, the special theory of relativity, or special relativity for short, is a scientific theory regarding the relationship between space and time. In Albert Einstein's original treatment, the theory is based on two postulates: # The laws of physics are invariant (that is, identical) in all inertial frames of reference (that is, frames of reference with no acceleration). # The speed of light in vacuum is the same for all observers, regardless of the motion of the light source or the observer. Origins and significance Special relativity was originally proposed by Albert Einstein in a paper published on 26 September 1905 titled "On the Electrodynamics of Moving Bodies".Albert Einstein (1905)''Zur Elektrodynamik bewegter Körper'', ''Annalen der Physik'' 17: 891; English translatioOn the Electrodynamics of Moving Bodiesby George Barker Jeffery and Wilfrid Perrett (1923); Another English translation On the Electrodynamics of Moving Bodies by Megh Nad Saha (1920). The incompa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Group Velocity
The group velocity of a wave is the velocity with which the overall envelope shape of the wave's amplitudes—known as the ''modulation'' or ''envelope'' of the wave—propagates through space. For example, if a stone is thrown into the middle of a very still pond, a circular pattern of waves with a quiescent center appears in the water, also known as a capillary wave. The expanding ring of waves is the wave group, within which one can discern individual waves that travel faster than the group as a whole. The amplitudes of the individual waves grow as they emerge from the trailing edge of the group and diminish as they approach the leading edge of the group. Definition and interpretation Definition The group velocity is defined by the equation: :v_ \ \equiv\ \frac\, where is the wave's angular frequency (usually expressed in radians per second), and is the angular wavenumber (usually expressed in radians per meter). The phase velocity is: . The function , which gi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phase Velocity
The phase velocity of a wave is the rate at which the wave propagates in any medium. This is the velocity at which the phase of any one frequency component of the wave travels. For such a component, any given phase of the wave (for example, the crest) will appear to travel at the phase velocity. The phase velocity is given in terms of the wavelength (lambda) and time period as :v_\mathrm = \frac. Equivalently, in terms of the wave's angular frequency , which specifies angular change per unit of time, and wavenumber (or angular wave number) , which represent the angular change per unit of space, :v_\mathrm = \frac. To gain some basic intuition for this equation, we consider a propagating (cosine) wave . We want to see how fast a particular phase of the wave travels. For example, we can choose , the phase of the first crest. This implies , and so . Formally, we let the phase and see immediately that and . So, it immediately follows that : \frac = -\frac \frac = \frac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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