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160-minute Solar Cycle
The 160-minute solar cycle was an apparent periodic oscillation in the solar surface which was observed in a number of early sets of data collected for helioseismology. The presence of a 160 minute cycle in the Sun is not substantiated by contemporary solar observations, and the historical signal is considered by mainstream scientists to occur as the redistribution of power from the diurnal cycle as a result of the observation window and atmospheric extinction. History The birth of helioseismology occurred in 1976 with the publications of papers from Brookes, Isaak and van der Raay and Severny, Kotov and Tsap, both of which reported upon the observation of a 160-minute solar oscillation with an amplitude of approximately two metres per second. It was rapidly realised that this frequency corresponded to one-ninth of a day, and therefore the authenticity of this signal was in some doubt. If a non-sinusoidal oscillation is present in a time-series then power will be seen in a pe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helioseismology
Helioseismology, a term coined by Douglas Gough, is the study of the structure and dynamics of the Sun through its oscillations. These are principally caused by sound waves that are continuously driven and damped by convection near the Sun's surface. It is similar to geoseismology, or asteroseismology (also coined by Gough), which are respectively the studies of the Earth or stars through their oscillations. While the Sun's oscillations were first detected in the early 1960s, it was only in the mid-1970s that it was realized that the oscillations propagated throughout the Sun and could allow scientists to study the Sun's deep interior. The modern field is separated into global helioseismology, which studies the Sun's resonant modes directly, and local helioseismology, which studies the propagation of the component waves near the Sun's surface. Helioseismology has contributed to a number of scientific breakthroughs. The most notable was to show the predicted neutrino flux from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Oscillation
Helioseismology, a term coined by Douglas Gough, is the study of the structure and dynamics of the Sun through its oscillations. These are principally caused by sound waves that are continuously driven and damped by convection near the Sun's surface. It is similar to geoseismology, or asteroseismology (also coined by Gough), which are respectively the studies of the Earth or stars through their oscillations. While the Sun's oscillations were first detected in the early 1960s, it was only in the mid-1970s that it was realized that the oscillations propagated throughout the Sun and could allow scientists to study the Sun's deep interior. The modern field is separated into global helioseismology, which studies the Sun's resonant modes directly, and local helioseismology, which studies the propagation of the component waves near the Sun's surface. Helioseismology has contributed to a number of scientific breakthroughs. The most notable was to show the predicted neutrino flux fro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Periodogram
In signal processing, a periodogram is an estimate of the spectral density of a signal. The term was coined by Arthur Schuster in 1898. Today, the periodogram is a component of more sophisticated methods (see spectral estimation). It is the most common tool for examining the amplitude vs frequency characteristics of FIR filters and window functions. FFT spectrum analyzers are also implemented as a time-sequence of periodograms. Definition There are at least two different definitions in use today. One of them involves time-averaging, and one does not. Time-averaging is also the purview of other articles ( Bartlett's method and Welch's method). This article is not about time-averaging. The definition of interest here is that the power spectral density of a continuous function, x(t), is the Fourier transform of its auto-correlation function (see Cross-correlation theorem, Spectral density#Power spectral density, and Wiener–Khinchin theorem): :\mathcal\ = X(f)\cdot X^*(f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BiSON
Bison are large bovines in the genus ''Bison'' (Greek: "wild ox" (bison)) within the tribe Bovini. Two extant and numerous extinct species are recognised. Of the two surviving species, the American bison, ''B. bison'', found only in North America, is the more numerous. Although colloquially referred to as a buffalo in the United States and Canada, it is only distantly related to the true buffalo. The North American species is composed of two subspecies, the Plains bison, ''B. b. bison'', and the wood bison, ''B. b. athabascae'', which is the namesake of Wood Buffalo National Park in Canada. A third subspecies, the eastern bison (''B. b. pennsylvanicus'') is no longer considered a valid taxon, being a junior synonym of ''B. b. bison''. References to "woods bison" or "wood bison" from the eastern United States refer to this subspecies, not ''B. b. athabascae'', which was not found in the region. The European bison, ''B. bonasus'', or wisent, or zubr, or colloquially European buff ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Global Oscillations Network Group
The Global Oscillation Network Group (GONG) is a worldwide network of six identical telescopes, designed to have 24/7 observations of the Sun. The network serves multiple purposes, including the provision of operation data for use in space weather prediction, and the study of solar internal structure and dynamics using helioseismology. Deployed in 1995, GONG is a set of six observing systems geographically distributed around the Earth so that the Sun can be observed as continuously as possible. The six observatories are the Teide Observatory ( Canary Islands), thLearmonth Solar Observatory(Western Australia), the Big Bear Solar Observatory (California), the Mauna Loa Solar Observatory (Hawaii), the Udaipur Solar Observatory (India) and the Cerro Tololo Inter-American Observatory (Chile). With these sites, GONG typically can observe the Sun 91% of the time, 24/7. GONG was constructed to provide observations for helioseismology, which aims to understand the solar interior by analy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar And Heliospheric Observatory
The Solar and Heliospheric Observatory (SOHO) is a European Space Agency (ESA) spacecraft built by a European industrial consortium led by Matra Marconi Space (now Airbus Defence and Space) that was launched on a Lockheed Martin Atlas IIAS launch vehicle on 2 December 1995, to study the Sun. It has also discovered over 4,000 comets.(2,703 discoveries as of 21 April 2014) It began normal operations in May 1996. It is a joint project between the (ESA) and . SOHO was part of the Interna ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
