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Electron Precipitation
Electron precipitation (also called energetic electron precipitation or EEP) is an atmospheric phenomenon that occurs when previously trapped electrons enter the Earth's atmosphere, thus creating communications interferences and other disturbances. Electrons trapped by Earth's magnetic field spiral around field lines to form the Van Allen radiation belt. The electrons are from the solar wind and may remain trapped above Earth for an indefinite period of time (in some cases years). When broadband very low frequency (VLF) waves propagate the radiation belts, the electrons exit the radiation belt and "precipitate" (or travel) into the ionosphere (a region of Earth's atmosphere) where the electrons will collide with ions. Electron precipitation is regularly linked to ozone depletion. It is often caused by lightning strikes. Process An electron's gyrofrequency is the number of times it revolves around a field line. VLF waves traveling through the magnetosphere, caused by lightning or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electron
The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no known components or substructure. The electron's mass is approximately 1/1836 that of the proton. Quantum mechanical properties of the electron include an intrinsic angular momentum ( spin) of a half-integer value, expressed in units of the reduced Planck constant, . Being fermions, no two electrons can occupy the same quantum state, in accordance with the Pauli exclusion principle. Like all elementary particles, electrons exhibit properties of both particles and waves: They can collide with other particles and can be diffracted like light. The wave properties of electrons are easier to observe with experiments than those of other particles like neutrons and protons because electrons have a lower mass and hence a longer de Broglie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Cycle
The solar cycle, also known as the solar magnetic activity cycle, sunspot cycle, or Schwabe cycle, is a nearly periodic 11-year change in the Sun's activity measured in terms of variations in the number of observed sunspots on the Sun's surface. Over the period of a solar cycle, levels of solar radiation and ejection of solar material, the number and size of sunspots, solar flares, and coronal loops all exhibit a synchronized fluctuation from a period of minimum activity to a period of a maximum activity back to a period of minimum activity. The magnetic field of the Sun flips during each solar cycle, with the flip occurring when the solar cycle is near its maximum. After two solar cycles, the Sun's magnetic field returns to its original state, completing what is known as a Hale cycle. This cycle has been observed for centuries by changes in the Sun's appearance and by terrestrial phenomena such as aurora but was not clearly identified until 1843. Solar activity, driven by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rockoon
A rockoon (from ''rocket'' and ''balloon'') is a solid fuel sounding rocket that, rather than being immediately lit while on the ground, is first carried into the upper atmosphere by a gas-filled balloon, then separated from the balloon and ignited. This allows the rocket to achieve a higher altitude, as the rocket does not have to move under power through the lower and thicker layers of the atmosphere. The original concept was developed by Cmdr. Lee Lewis, Cmdr. G. Halvorson, S. F. Singer, and James A. Van Allen during the Aerobee rocket firing cruise of the U.S.S. ''Norton Sound'' on March 1, 1949. A serious disadvantage is that unpiloted balloons cannot be steered, and consequently the location from which the rocket is launched can be uncertain. Therefore, a large area for the fall of the rocket is required for safety reasons. Early atmospheric research ''Time'' magazine reported in 1959: "Van Allen's 'Rockoons' could not be fired in Iowa for fear that the spent rocket ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
James Van Allen
James Alfred Van Allen (September 7, 1914August 9, 2006) was an American space scientist at the University of Iowa. He was instrumental in establishing the field of magnetospheric research in space. The Van Allen radiation belts were named after him, following his discovery using Geiger–Müller tube instruments on the 1958 satellites (Explorer 1, Explorer 3, and Pioneer 3) during the International Geophysical Year. Van Allen led the scientific community in putting scientific research instruments on space satellites. Early years and education Van Allen was born on 7 September 1914 on a small farm near Mount Pleasant, Iowa. As a child, he was fascinated by mechanical and electrical devices and was an avid reader of ''Popular Mechanics'' and ''Popular Science'' magazines. He once horrified his mother by constructing a Tesla coil that produced foot-long sparks and caused his hair to stand on end. A fellowship allowed him to continue studying nuclear physics at the Carnegie I ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X-ray
An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz ( to ) and energies in the range 145 eV to 124 keV. X-ray wavelengths are shorter than those of UV rays and typically longer than those of gamma rays. In many languages, X-radiation is referred to as Röntgen radiation, after the German scientist Wilhelm Conrad Röntgen, who discovered it on November 8, 1895. He named it ''X-radiation'' to signify an unknown type of radiation.Novelline, Robert (1997). ''Squire's Fundamentals of Radiology''. Harvard University Press. 5th edition. . Spellings of ''X-ray(s)'' in English include the variants ''x-ray(s)'', ''xray(s)'', and ''X ray(s)''. The most familiar use of X-rays is checking for fractures (broken bones), but X-rays are also used in other ways. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aura (satellite)
Aura (EOS CH-1) is a multi-national NASA scientific research satellite in orbit around the Earth, studying the Earth's ozone layer, air quality and climate. It is the third major component of the Earth Observing System (EOS) following on Terra (launched 1999) and Aqua (launched 2002). Aura follows on from the Upper Atmosphere Research Satellite (UARS). Aura is a joint mission between NASA, the Netherlands, Finland, and the U.K. The Aura spacecraft is healthy and is expected to operate until at least 2022, likely beyond. The name "Aura" comes from the Latin word for air. The satellite was launched from Vandenberg Air Force Base on July 15, 2004, aboard a Delta II 7920-10L rocket. The Aura spacecraft has a mass of about . The body is long with the extended single solar panel about long. Aura flies in a sun-synchronous orbit, in formation with 3 other satellites, collectively known as the " A Train"; it is last in the formation. The other satellites in the formation ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microwave Limb Sounder
The microwave limb sounder (MLS) experiments measure (naturally occurring) microwave thermal emission from the limb (edge) of Earth's upper atmosphere. The data is used to create vertical profiles of atmospheric gases, temperature, pressure, and cloud ice. History * 12 September 1991 – NASA launches Upper Atmosphere Research Satellite (UARS) STS-48 mission, largely in response to threat of chlorofluorocarbons to ozone layer. * 15 July 2004 – NASA launches Earth Observing System (EOS) Aura mission with overall scientific objectives of determining whether global stratospheric ozone is recovering, measuring composition effects on climate variability, and studying pollution in the upper troposphere. See also * Remote sensing * Jet Propulsion Laboratory The Jet Propulsion Laboratory (JPL) is a Federally funded research and development centers, federally funded research and development center and NASA field center in the City of La Cañada Flintridge, California, La Cañada Fl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiometer
A radiometer or roentgenometer is a device for measuring the radiant flux (power) of electromagnetic radiation. Generally, a radiometer is an infrared radiation detector or an ultraviolet detector. Microwave radiometers operate in the microwave wavelengths. While the term ''radiometer'' can refer to any device that measures electromagnetic radiation (e.g. light), the term is often used to refer specifically to a Crookes radiometer ("light-mill"), a device invented in 1873 in which a rotor (having vanes which are dark on one side, and light on the other) in a partial vacuum spins when exposed to light. A common belief (one originally held even by Crookes) is that the momentum of the absorbed light on the black faces makes the radiometer operate. If this were true, however, the radiometer would spin away from the non-black faces, since the photons bouncing off those faces impart more momentum than the photons absorbed on the black faces. Photons do exert radiation pressure on t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Occultation
An occultation is an event that occurs when one object is hidden from the observer by another object that passes between them. The term is often used in astronomy, but can also refer to any situation in which an object in the foreground blocks from view (occults) an object in the background. In this general sense, occultation applies to the visual scene observed from low-flying aircraft (or computer-generated imagery) when foreground objects obscure distant objects dynamically, as the scene changes over time. If the closer body does not entirely conceal the farther one, the event is called a '' transit''. Both transit and occultation may be referred to generally as ''occlusion''; and if a shadow is cast onto the observer, it is called an eclipse. The symbol for an occultation, and especially a solar eclipse, is file:Occultation symbol.svg (U+1F775 🝵). Occultations by the Moon The term occultation is most frequently used to describe lunar occultations, those relati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Envisat
Envisat ("Environmental Satellite") is a large inactive Earth-observing satellite which is still in orbit and now considered space debris. Operated by the European Space Agency (ESA), it was the world's largest civilian Earth observation satellite. It was launched on 1 March 2002 aboard an Ariane 5 from the Guyana Space Centre in Kourou, French Guiana, into a Sun synchronous polar orbit at an altitude of 790 ± 10 km. It orbits the Earth in about 101 minutes, with a repeat cycle of 35 days. After losing contact with the satellite on 8 April 2012, ESA formally announced the end of Envisat's mission on 9 May 2012. Envisat cost 2.3 billion Euro (including 300 million Euro for 5 years of operations) to develop and launch. The mission has been replaced by the Sentinel series of satellites. The first of these, Sentinel 1, has taken over the radar duties of Envisat since its launch in 2014. Mission Envisat was launched as an Earth observation satellite. Its obj ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Global Ozone Monitoring By Occultation Of Stars
Global Ozone Monitoring by Occultation of Stars (GOMOS), is an instrument on board the European satellite Envisat launched 1 March 2002. It is the first space instrument dedicated to the study of the atmosphere of the Earth by the technique of stellar occultation. The spectrum of stars in the ultraviolet, visible and the near infrared parts of the electromagnetic spectrum is observed. It is aimed to use GOMOS to build a climatology of ozone and related species in the middle atmosphere (15 to 100 km). Instrument details The 250-680 nm spectral domain is used for the determination of O3, NO2, NO3−, aerosols and temperature. In addition, two high spectral resolution channels centred at 760 and 940 nm allow measurements of O2 and H2O and two fast photometers are used to correct star scintillation perturbations and to determine high vertical resolution temperature profiles. Global latitude coverage is obtained with up to 40 stellar occultations per orbit I ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Superposed Epoch Analysis
Superposed epoch analysis (SPE or SEA), also called Chree analysis after a paper by Charles Chree that employed the technique, is a statistical tool used in data analysis either to detect periodicities within a time sequence or to reveal a correlation (usually in time) between two data sequences (usually two time series). When comparing two time series, the essence of the method is to: (1) define each occurrence of an event in one data sequence (series #1) as a key time; (2) extract subsets of data from the other sequence (series #2) within some time range near each key time; (3) superpose all extracted subsets from series #2 (with key times for all subsets synchronized) by adding them. (To effectively superpose data from series #2 that are recorded at different or even irregular times, data binning is often used.) This approach can be used to detect a signal (i.e., related variations in both series) in the presence of noise (i.e., unrelated variations in both series) whene ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
