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42-713: The mathematician Sydney Chapman introduced the term aeronomy to describe the study of the Earth's upper atmosphere in 1946 in a letter to the editor of Nature entitled "Some Thoughts on Nomenclature." The term became official in 1954 when the International Union of Geodesy and Geophysics adopted it. "Aeronomy" later also began to refer to the study of the corresponding regions of the atmospheres of other planets. Aeronomy can be divided into three main branches: terrestrial aeronomy , planetary aeronomy , and comparative aeronomy . Terrestrial aeronomy focuses on

84-431: A computer . Recent advances have seen increasing reliance of computational algorithms in a range of miniaturised spectrometers without diffraction gratings, for example, through the use of quantum dot-based filter arrays on to a CCD chip or a series of photodetectors realised on a single nanostructure. Joseph von Fraunhofer developed the first modern spectroscope by combining a prism, diffraction slit and telescope in

126-471: A gas cloud, and these absorption lines can also identify chemical compounds. Much of our knowledge of the chemical makeup of the universe comes from spectra. Spectroscopes are often used in astronomy and some branches of chemistry . Early spectroscopes were simply prisms with graduations marking wavelengths of light. Modern spectroscopes generally use a diffraction grating , a movable slit , and some kind of photodetector , all automated and controlled by

168-433: A low pressure sodium vapor lamp . In the original spectroscope design in the early 19th century, light entered a slit and a collimating lens transformed the light into a thin beam of parallel rays. The light then passed through a prism (in hand-held spectroscopes, usually an Amici prism ) that refracted the beam into a spectrum because different wavelengths were refracted different amounts due to dispersion . This image

210-464: A manner that increased the spectral resolution and was reproducible in other laboratories. Fraunhofer also went on to invent the first diffraction spectroscope. Gustav Robert Kirchhoff and Robert Bunsen discovered the application of spectroscopes to chemical analysis and used this approach to discover caesium and rubidium . Kirchhoff and Bunsen's analysis also enabled a chemical explanation of stellar spectra , including Fraunhofer lines . When

252-502: A material is heated to incandescence it emits light that is characteristic of the atomic makeup of the material. Particular light frequencies give rise to sharply defined bands on the scale which can be thought of as fingerprints. For example, the element sodium has a very characteristic double yellow band known as the Sodium D-lines at 588.9950 and 589.5924 nanometers, the color of which will be familiar to anyone who has seen

294-447: A multi-channel detector system or camera that detects and records the spectrum of light. The term was first used in 1876 by Dr. Henry Draper when he invented the earliest version of this device, and which he used to take several photographs of the spectrum of Vega . This earliest version of the spectrograph was cumbersome to use and difficult to manage. There are several kinds of machines referred to as spectrographs , depending on

336-446: A scholarship to Trinity College, Cambridge . He was at first awarded only a partial scholarship as a sizar (meaning that he obtained financial support by acting as a servant to other students), but from his second year onwards he received a full scholarship. He graduated as a wrangler in 1910. He began his research in pure mathematics under G. H. Hardy , but later that year was asked by Sir Frank Dyson to be his chief assistant at

378-455: A slit is used and a CCD-chip records the spectrum. Both gratings have a wide spacing, and one is blazed so that only the first order is visible and the other is blazed with many higher orders visible, so a very fine spectrum is presented to the CCD. In conventional spectrographs, a slit is inserted into the beam to limit the image extent in the dispersion direction. A slitless spectrograph omits

420-425: A wide range of non-optical wavelengths, from gamma rays and X-rays into the far infrared . If the instrument is designed to measure the spectrum on an absolute scale rather than a relative one, then it is typically called a spectrophotometer . The majority of spectrophotometers are used in spectral regions near the visible spectrum. A spectrometer that is calibrated for measurement of the incident optical power

462-449: Is called a spectroradiometer . In general, any particular instrument will operate over a small portion of this total range because of the different techniques used to measure different portions of the spectrum. Below optical frequencies (that is, at microwave and radio frequencies), the spectrum analyzer is a closely related electronic device. Spectrometers are used in many fields. For example, they are used in astronomy to analyze

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504-404: Is essential to an understanding of the atmosphere as a whole and of benefit in improving the understanding of meteorology. Modeling and observations of atmospheric tides allow researchers to monitor and predict changes in the Earth's atmosphere. "Upper-atmospheric lightning" or "upper-atmospheric discharge" are terms aeronomers sometimes use to refer to a family of electrical-breakdown phenomena in

546-535: Is most often the irradiance of the light but could also, for instance, be the polarization state. The independent variable is usually the wavelength of the light or a closely derived physical quantity, such as the corresponding wavenumber or the photon energy, in units of measurement such as centimeters, reciprocal centimeters , or electron volts , respectively. A spectrometer is used in spectroscopy for producing spectral lines and measuring their wavelengths and intensities. Spectrometers may operate over

588-765: Is named in his honour, as is the Sydney Chapman Building on the campus of the University of Alaska Fairbanks . This building served as the first permanent home of the University of Alaska Geophysical Institute, and it now contains the Department of Computer Science and the Department of Mathematics and Statistics. The American Geophysical Union organises "Chapman Conferences," which are small, topical meetings intended to foster innovative research in key areas. The Royal Astronomical Society founded

630-610: Is sometimes called polychromator , as an analogy to monochromator . The star spectral classification and discovery of the main sequence , Hubble's law and the Hubble sequence were all made with spectrographs that used photographic paper. James Webb Space Telescope contains both a near-infrared spectrograph ( NIRSpec ) and a mid-infrared spectrograph ( MIRI ). An echelle -based spectrograph uses two diffraction gratings , rotated 90 degrees with respect to each other and placed close to one another. Therefore, an entrance point and not

672-558: The Chapman Medal in his memory. In 1970, Chapman died in Boulder, Colorado , at the age of 82. His wife died in 1967. Optical spectrometer An optical spectrometer ( spectrophotometer , spectrograph or spectroscope ) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum , typically used in spectroscopic analysis to identify materials. The variable measured

714-454: The Explorer 12 satellite . In 1940, Chapman and a German colleague Julius Bartels published a book in two volumes on geomagnetism, which was to become the standard text book for the next two decades. In 1946 Chapman coined the term: Aeronomy , which is used today to describe the scientific field of high-altitude research into atmosphere/space interaction. From 1951 to 1954, Chapman

756-681: The Royal Greenwich Observatory . From 1914 to 1919, Chapman returned to Cambridge as a lecturer in mathematics and a fellow of Trinity. He held the Beyer Chair of Applied Mathematics at Manchester from 1919 to 1924, the same position as had been held by Lamb, and then moved to Imperial College London . During the Second World War he was Deputy Scientific Advisor to the Army Council. In 1946, Chapman

798-538: The Earth's upper atmosphere that occur well above the altitudes of the tropospheric lightning observed in the lower atmosphere. Currently, the preferred term for an electrical-discharge phenomenon induced in the upper atmosphere by tropospheric lightning is " transient luminous event " (TLE). There are various types of TLEs including red sprites, sprite halos, blue jets, and ELVES (an acronym for " Emission of Light and Very-Low-Frequency perturbations due to Electromagnetic Pulse Sources"). Planetary aeronomy studies

840-608: The Earth's upper atmosphere, which extends from the stratopause to the atmosphere's boundary with outer space and is defined as consisting of the mesosphere , thermosphere , and exosphere and their ionized component, the ionosphere . Terrestrial aeronomy contrasts with meteorology , which is the scientific study of the Earth's lower atmosphere, defined as the troposphere and stratosphere . Although terrestrial aeronomy and meteorology once were completely separate fields of scientific study, cooperation between terrestrial aeronomers and meteorologists has grown as discoveries made since

882-638: The Russian Andrey Kolmogorov independently developed the pivotal set of equations in the field, the Chapman–Kolmogorov equations . Chapman is credited with working out, in 1930, the photochemical mechanisms that give rise to the ozone layer . Chapman is recognised as one of the pioneers of solar-terrestrial physics. This interest stemmed from his early work on the kinetic theory of gases. Chapman studied magnetic storms and aurorae , developing theories to explain their relation to

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924-683: The University of Alaska Geophysical Institute from 1951 to 1970, he spent three months of the year in Alaska , usually during winter for research into auroras. Much of the remainder of the year he spent at the High Altitude Observatory in Boulder, Colorado. Chapman's most noted mathematical accomplishments were in the field of stochastic processes (random processes), especially Markov processes . In his study of Markovian stochastic processes and their generalizations, Chapman and

966-406: The absorption spectra of gemstones, thereby allowing them to make inferences about what kind of gem they are examining. A gemologist may compare the absorption spectrum they observe with a catalogue of spectra for various gems to help narrow down the exact identity of the gem. A spectrograph is an instrument that separates light into its wavelengths and records the data. A spectrograph typically has

1008-445: The atmospheres of those planets as well. Comparative aeronomy uses the findings of terrestrial and planetary aeronomy — traditionally separate scientific fields — to compare the characteristics and behaviors of the atmospheres of other planets with one another and with the upper atmosphere of Earth. It seeks to identify and describe the ways in which differing chemistry, magnetic fields , and thermodynamics on various planets affect

1050-494: The atmospheres of those planets through the use of instruments such as interferometers , optical spectrometers , magnetometers , and plasma detectors and techniques such as radio occultation . Although planetary aeronomy originally was confined to the study of the atmospheres of the other planets in the Solar System , the discovery since 1995 of exoplanets has allowed planetary aeronomers to expand their field to include

1092-491: The camera, allowing real-time spectrographic analysis with far greater accuracy. Arrays of photosensors are also used in place of film in spectrographic systems. Such spectral analysis, or spectroscopy, has become an important scientific tool for analyzing the composition of unknown material and for studying astronomical phenomena and testing astronomical theories. In modern spectrographs in the UV, visible, and near-IR spectral ranges,

1134-457: The creation, evolution, diversity, and disappearance of atmospheres. Sydney Chapman (mathematician) Sydney Chapman FRS (29 January 1888 – 16 June 1970) was a British mathematician and geophysicist . His work on the kinetic theory of gases , solar-terrestrial physics , and the Earth 's ozone layer has inspired a broad range of research over many decades. Chapman

1176-539: The department headed by Osborne Reynolds . Chapman was taught mathematics by Horace Lamb , the Beyer professor of mathematics, and J. E. Littlewood , who came from Cambridge in Chapman's final year at Manchester. Although he graduated with an engineering degree, Chapman had become so enthusiastic for mathematics that he stayed for one further year to take a mathematics degree. Following Lamb's suggestion, Chapman applied for

1218-533: The early 1990s have demonstrated that the upper and lower atmospheres have an impact on one another's physics , chemistry , and biology . Terrestrial aeronomers study atmospheric tides and upper-atmospheric lightning discharges such as red sprites , sprite halos, blue jets , and ELVES. They also investigate the causes of dissociation and ionization processes in the Earth's upper atmosphere. Terrestrial aeronomers use ground-based telescopes , balloons , satellites , and sounding rockets to gather data from

1260-679: The first satellite launches. Chapman was bestowed many honours over his career, including Smith's Prize in 1913, election as a Fellow of the Royal Society in 1919, Invited Speaker of the ICM in 1924, Royal Society Bakerian lecturer in 1931, Royal Society Royal Medal in 1934, London Mathematical Society De Morgan Medal in 1944. In 1949, he was awarded the Gold Medal of the Royal Astronomical Society and

1302-421: The interaction of the Earth's magnetic field with the solar wind . He disputed and ridiculed the work of Kristian Birkeland and Hannes Alfvén , later adopting Birkeland's theories as his own. Chapman and his first graduate student , V. C. A. Ferraro, predicted the presence of the magnetosphere in the early 1930s. They also predicted characteristics of the magnetosphere that were confirmed 30 years later by

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1344-424: The precise nature of the waves. The first spectrographs used photographic paper as the detector. The plant pigment phytochrome was discovered using a spectrograph that used living plants as the detector. More recent spectrographs use electronic detectors, such as CCDs which can be used for both visible and UV light. The exact choice of detector depends on the wavelengths of light to be recorded. A spectrograph

1386-486: The radiation from objects and deduce their chemical composition. The spectrometer uses a prism or a grating to spread the light into a spectrum. This allows astronomers to detect many of the chemical elements by their characteristic spectral lines. These lines are named for the elements which cause them, such as the hydrogen alpha , beta, and gamma lines. A glowing object will show bright spectral lines. Dark lines are made by absorption, for example by light passing through

1428-428: The regions of the atmospheres of other planets that correspond to the Earth's mesosphere, thermosphere, exosphere, and ionosphere. In some cases, a planet's entire atmosphere may consist only of what on Earth constitutes the upper atmosphere, or only a portion of it. Planetary aeronomers use ground-based telescopes, space telescopes , and space probes which fly by , orbit , or land on other planets to gain knowledge of

1470-452: The slit; this results in images that convolve the image information with spectral information along the direction of dispersion. If the field is not sufficiently sparse, then spectra from different sources in the image field will overlap. The trade is that slitless spectrographs can produce spectral images much more quickly than scanning a conventional spectrograph. That is useful in applications such as solar physics where time evolution

1512-487: The spectrum is generally given in the form of photon number per unit wavelength (nm or μm), wavenumber (μm , cm ), frequency (THz), or energy (eV), with the units indicated by the abscissa . In the mid- to far-IR, spectra are typically expressed in units of Watts per unit wavelength (μm) or wavenumber (cm ). In many cases, the spectrum is displayed with the units left implied (such as "digital counts" per spectral channel). Gemologists frequently use spectroscopes to determine

1554-471: The upper atmosphere. Atmospheric tides are global-scale periodic oscillations of the Earth′s atmosphere, analogous in many ways to ocean tides . Atmospheric tides dominate the dynamics of the mesosphere and lower thermosphere, serving as an important mechanism for transporting energy from the upper atmosphere into the lower atmosphere. Terrestrial aeronomers study atmospheric tides because an understanding of them

1596-569: Was born in Eccles , near Salford in England and began his advanced studies at a technical institute, now the University of Salford , in 1902. In 1904 at age 16, Chapman entered the University of Manchester . He competed for a scholarship to the university offered by his home county, and was the last student selected. Chapman later reflected, "I sometimes wonder what would have happened if I'd hit one place lower." He initially studied engineering in

1638-951: Was elected as a Fellow of the Royal Society of Edinburgh in 1953. In 1964, he was awarded the Copley Medal of the Royal Society and in 1965 the Symons Gold Medal of the Royal Meteorological Society . He was elected to the National Academies of Science of the United States, Norway, Sweden and Finland. He served as president of the London Mathematical Society during 1929–1931 and the Royal Meteorological Society 1932–1933. The lunar Crater Chapman

1680-562: Was elected to the Sedleian Chair of Natural Philosophy at Oxford, and was appointed fellow of The Queen's College, Oxford . In 1953, on his retirement from Oxford, Chapman took research and teaching opportunities all over the world, including at the University of Alaska and the University of Colorado , but also as far afield as Istanbul , Cairo , Prague, and Tokyo. As the Advisory Scientific Director of

1722-620: Was president of the International Union of Geodesy and Geophysics (IUGG). Chapman was President of the Special Committee for the International Geophysical Year (IGY). The idea of the IGY stemmed from a discussion in 1950 between Chapman and scientists including James Van Allen . The IGY was held in 1957–58, and resulted in great progress in fields including Earth and space sciences, as well as leading to

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1764-415: Was then viewed through a tube with a scale that was transposed upon the spectral image, enabling its direct measurement. With the development of photographic film , the more accurate spectrograph was created. It was based on the same principle as the spectroscope, but it had a camera in place of the viewing tube. In recent years, the electronic circuits built around the photomultiplier tube have replaced

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