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Critical Ionization Velocity
Critical ionization velocity (CIV), or critical velocity (CV), is the relative velocity between a neutral gas and plasma (an ionized gas), at which the neutral gas will start to ionize. If more energy is supplied, the velocity of the atoms or molecules will not exceed the critical ionization velocity until the gas becomes almost fully ionized. The phenomenon was predicted by Swedish engineer and plasma scientist, Hannes Alfvén, in connection with his model on the origin of the Solar System (1942). At the time, no known mechanism was available to explain the phenomenon, but the theory was subsequently demonstrated in the laboratory.U.V. Fahleson, "Experiments with plasma moving through neutral gas", Phys. Fluids, 4 123 (1961) Subsequent research by Brenning and Axnäs (1988) have suggested that a ''lower hybrid'' plasma instability is involved in transferring energy from the larger ions to electrons so that they have sufficient energy to ionize. Application of the theory to astron ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plasma (physics)
Plasma () 1, where \nu_ is the electron gyrofrequency and \nu_ is the electron collision rate. It is often the case that the electrons are magnetized while the ions are not. Magnetized plasmas are ''anisotropic'', meaning that their properties in the direction parallel to the magnetic field are different from those perpendicular to it. While electric fields in plasmas are usually small due to the plasma high conductivity, the electric field associated with a plasma moving with velocity \mathbf in the magnetic field \mathbf is given by the usual Lorentz force, Lorentz formula \mathbf = -\mathbf\times\mathbf, and is not affected by Debye shielding. Mathematical descriptions To completely describe the state of a plasma, all of the particle locations and velocities that describe the electromagnetic field in the plasma region would need to be written down. However, it is generally not practical or necessary to keep track of all the particles in a plasma. Therefore, plasma physicist ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ionize
Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule is called an ion. Ionization can result from the loss of an electron after collisions with subatomic particles, collisions with other atoms, molecules and ions, or through the interaction with electromagnetic radiation. Heterolytic bond cleavage and heterolytic substitution reactions can result in the formation of ion pairs. Ionization can occur through radioactive decay by the internal conversion process, in which an excited nucleus transfers its energy to one of the inner-shell electrons causing it to be ejected. Uses Everyday examples of gas ionization are such as within a fluorescent lamp or other electrical discharge lamps. It is also used in radiation detectors such as the Geiger-Müller counter or the ionization chamber. The ionizati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hannes Alfvén
Hannes Olof Gösta Alfvén (; 30 May 1908 – 2 April 1995) was a Swedish electrical engineer, plasma physicist and winner of the 1970 Nobel Prize in Physics for his work on magnetohydrodynamics (MHD). He described the class of MHD waves now known as Alfvén waves. He was originally trained as an electrical power engineer and later moved to research and teaching in the fields of plasma physics and electrical engineering. Alfvén made many contributions to plasma physics, including theories describing the behavior of aurorae, the Van Allen radiation belts, the effect of magnetic storms on the Earth's magnetic field, the terrestrial magnetosphere, and the dynamics of plasmas in the Milky Way galaxy. Education Alfvén received his PhD from the University of Uppsala in 1934. His thesis was titled "Investigations of High-frequency Electromagnetic Waves." Early years In 1934, Alfvén taught physics at both the University of Uppsala and the Nobel Institute for Physics (late ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar System" and "solar system" structures in theinaming guidelines document. The name is commonly rendered in lower case ('solar system'), as, for example, in the ''Oxford English Dictionary'' an''Merriam-Webster's 11th Collegiate Dictionary''. is the gravity, gravitationally bound system of the Sun and the objects that orbit it. It Formation and evolution of the Solar System, formed 4.6 billion years ago from the gravitational collapse of a giant interstellar molecular cloud. The solar mass, vast majority (99.86%) of the system's mass is in the Sun, with most of the Jupiter mass, remaining mass contained in the planet Jupiter. The four inner Solar System, inner system planets—Mercury (planet), Mercury, Venus, Earth and Mars—are terrest ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lower Hybrid Oscillation
In plasma physics, a lower hybrid oscillation is a longitudinal oscillation of ions and electrons in a magnetized plasma. The direction of propagation must be very nearly perpendicular to the stationary magnetic field, within about radians. Otherwise the electrons can move along the field lines fast enough to shield the oscillations in potential. The frequency of oscillation is :\omega = \Omega_i\Omega_e)^+\omega_^, where Ωi is the ion cyclotron frequency, Ωe is the electron cyclotron frequency and ωpi is the ion plasma frequency. This is the lower hybrid frequency, so called because it is a "hybrid", or mixture, of two frequencies. There are also an upper hybrid frequency and upper hybrid oscillation. The lower hybrid oscillation is unusual in that the ion and electron masses play an equally important role. This mode is relatively unimportant in practice because the necessary precise orientation relative to the magnetic field is seldom achieved. Exceptions are the use of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Instability
In numerous fields of study, the component of instability within a system is generally characterized by some of the outputs or internal states growing without bounds. Not all systems that are not stable are unstable; systems can also be marginally stable or exhibit limit cycle behavior. In structural engineering, a structure can become unstable when excessive load is applied. Beyond a certain threshold, structural deflections magnify stresses, which in turn increases deflections. This can take the form of buckling or crippling. The general field of study is called structural stability. Atmospheric instability is a major component of all weather systems on Earth. Instability in control systems In the theory of dynamical systems, a state variable in a system is said to be unstable if it evolves without bounds. A system itself is said to be unstable if at least one of its state variables is unstable. In continuous time control theory, a system is unstable if any of the ro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dense Plasma Focus
A dense plasma focus (DPF) is a type of plasma generating system originally developed as a fusion power device starting in the early 1960s. The system demonstrated scaling laws that suggested it would not be useful in the commercial power role, and since the 1980s it has been used primarily as a fusion teaching system, and as a source of neutrons and X-rays. The original concept was developed in 1954 by N.V. Filippov, who noticed the effect while working on early pinch machines in the USSR. A major research program on DPF was carried out in the USSR through the late 1950s, and continues to this day. A different version of the same basic concept was independently discovered in the US by J.W. Mather in the early 1960s. This version saw some development in the 1970s, and variations continue to be developed. The basic design derives from the z-pinch concept. Both the DPF and pinch use large electrical currents run through a gas to cause it to ionize into a plasma and then '' pinch'' do ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coronal Mass Ejection
A coronal mass ejection (CME) is a significant release of plasma and accompanying magnetic field from the Sun's corona into the heliosphere. CMEs are often associated with solar flares and other forms of solar activity, but a broadly accepted theoretical understanding of these relationships has not been established. If a CME enters interplanetary space, it is referred to as an interplanetary coronal mass ejection (ICME). ICMEs are capable of reaching and colliding with Earth's magnetosphere, where they can cause geomagnetic storms, aurorae, and in rare cases damage to electrical power grids. The largest recorded geomagnetic perturbation, resulting presumably from a CME, was the solar storm of 1859. Also known as the Carrington Event, it disabled parts of the at the time newly created United States telegraph network, starting fires and shocking some telegraph operators. Near solar maxima, the Sun produces about three CMEs every day, whereas near solar minima, there is about ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Flare
A solar flare is an intense localized eruption of electromagnetic radiation in the Sun's atmosphere. Flares occur in active regions and are often, but not always, accompanied by coronal mass ejections, solar particle events, and other solar phenomena. The occurrence of solar flares varies with the 11-year solar cycle. Solar flares are thought to occur when stored magnetic energy in the Sun's atmosphere accelerates charged particles in the surrounding plasma. This results in the emission of electromagnetic radiation across the electromagnetic spectrum. High-energy electromagnetic radiation from solar flares is absorbed by the daylight side of Earth's upper atmosphere, in particular the ionosphere, and does not reach the surface. This absorption can temporarily increase the ionization of the ionosphere which may interfere with short-wave radio communication. The prediction of solar flares is an active area of research. Flares also occur on other stars, where the term ''stellar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anthony Peratt
Anthony L. Peratt is an American physicist whose most notable achievements have been in plasma discharge petroglyphs, plasma physics, nuclear fusion and the monitoring of nuclear weapons. Education Peratt was a graduate student of Nobel Prize winning Hannes Alfvén. He received a Ph.D in electrical engineering / plasma physics in 1971 from the University of Southern California (USC), Los Angeles. He was awarded a Master of Science in electrical engineering in 1967, also from USC. Addendum tClass Of 2009: The Newly Elected Members Of AdCom in the same issue of the newsletter. Scientific career He worked at the Lawrence Livermore National Laboratory between 1972 and 1979, during which time he held the position of a Guest Physicist at the Max Planck Institute for Physics and Astrophysics at Garching, near Munich, from 1975 to 1977. From 1981 to the present he has worked at the Los Alamos National Laboratory, serving in the Applied Theoretical Physics Division. He had a sabbatica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gerrit Verschuur
Gerrit L. Verschuur (born in 1937 in Cape Town, South Africa) is an American scientist who is best known for his work in radio astronomy. Though a pioneer in that field, Verschuur is also an author (he has written about astronomy, natural disasters, and earth sciences), inventor, adjunct professor of physics for the University of Memphis. Since 1996 he has been the Chief Scientist for Translucent Technologies, LLC; a company which is based in Memphis, Tennessee.Uncommonly Lakeland In 1992 Verschuur became a resident of the City of Lakeland, which is located in [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
