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Spheromak LLNL
A spheromak is an arrangement of plasma formed into a toroidal shape similar to a smoke ring. The spheromak contains large internal electric currents and their associated magnetic fields arranged so the magnetohydrodynamic forces within the spheromak are nearly balanced, resulting in long-lived ( microsecond) confinement times without external fields. Spheromaks belong to a type of plasma configuration referred to as the compact toroids. A spheromak can be made and sustained using magnetic flux injection, leading to a dynomak. The physics of the spheromak and of collisions between spheromaks is similar to a variety of astrophysical events, like coronal loops and filaments, relativistic jets and plasmoids. They are particularly useful for studying magnetic reconnection events, when two or more spheromaks collide. Spheromaks are easy to generate using a "gun" that ejects spheromaks off the end of an electrode into a holding area, called the flux conserver. This has made them ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spheromak Formation In Dynomak - Model
A spheromak is an arrangement of plasma formed into a toroidal shape similar to a smoke ring. The spheromak contains large internal electric currents and their associated magnetic fields arranged so the magnetohydrodynamic forces within the spheromak are nearly balanced, resulting in long-lived (microsecond) confinement times without external fields. Spheromaks belong to a type of plasma configuration referred to as the compact toroids. A spheromak can be made and sustained using magnetic flux injection, leading to a dynomak. The physics of the spheromak and of collisions between spheromaks is similar to a variety of astrophysical events, like coronal loops and filaments, relativistic jets and plasmoids. They are particularly useful for studying magnetic reconnection events, when two or more spheromaks collide. Spheromaks are easy to generate using a "gun" that ejects spheromaks off the end of an electrode into a holding area, called the flux conserver. This has made ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astrophysics
Astrophysics is a science that employs the methods and principles of physics and chemistry in the study of astronomical objects and phenomena. As one of the founders of the discipline said, Astrophysics "seeks to ascertain the nature of the heavenly bodies, rather than their positions or motions in space–''what'' they are, rather than ''where'' they are." Among the subjects studied are the Sun, other stars, galaxies, extrasolar planets, the interstellar medium and the cosmic microwave background. Emissions from these objects are examined across all parts of the electromagnetic spectrum, and the properties examined include luminosity, density, temperature, and chemical composition. Because astrophysics is a very broad subject, ''astrophysicists'' apply concepts and methods from many disciplines of physics, including classical mechanics, electromagnetism, statistical mechanics, thermodynamics, quantum mechanics, relativity, nuclear and particle physics, and atomic and m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lodewijk Woltjer
Lodewijk Woltjer (26 April 1930 – 25 August 2019) was an astronomer, and the son of astronomer Jan Woltjer. He studied at the University of Leiden under Jan Oort earning a PhD in astronomy in 1957 with a thesis on the Crab Nebula. This was followed by post-doctoral research appointments to various American universities and the subsequent appointment of professor of theoretical astrophysics and plasma physics in the University of Leiden. From 1964 to 1974 he was Rutherford Professor of Astronomy and Chair of the Astronomy Department at Columbia University in New York. From 1975 to 1987 he was Director General of the European Southern Observatory (ESO), where he initiated the construction of the Very Large Telescope. In 1994–1997 he was President of the International Astronomical Union. Woltjer was honored in 1987 with the Karl Schwarzschild Medal. He was the first Editor-in-Chief of The Astronomy and Astrophysics Review, inaugurated in 1989; and also the Editor of the Astronomi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lundquist Number
In plasma physics, the Lundquist number (denoted by S) is a dimensionless ratio which compares the timescale of an Alfvén wave crossing to the timescale of resistive diffusion. It is a special case of the magnetic Reynolds number when the Alfvén velocity is the typical velocity scale of the system, and is given by :S = \frac , where L is the typical length scale of the system, \eta is the magnetic diffusivity and v_A is the Alfvén velocity of the plasma. High Lundquist numbers indicate highly conducting plasmas, while low Lundquist numbers indicate more resistive plasmas. Laboratory plasma experiments typically have Lundquist numbers between 10^2-10^8, while in astrophysical situations the Lundquist number can be greater than 10^. Considerations of Lundquist number are especially important in magnetic reconnection. See also * Magnetic Prandtl number * Péclet number In continuum mechanics, the Péclet number (, after Jean Claude Eugène Péclet) is a class of dimensi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver and was formerly named hydrargyrum ( ) from the Greek words, ''hydor'' (water) and ''argyros'' (silver). A heavy, silvery d-block A block of the periodic table is a set of elements unified by the atomic orbitals their valence electrons or vacancies lie in. The term appears to have been first used by Charles Janet. Each block is named after its characteristic orbital: s-blo ... element, mercury is the only metallic element that is known to be liquid at standard temperature and pressure; the only other element that is liquid under these conditions is the halogen bromine, though metals such as caesium, gallium, and rubidium melt just above room temperature. Mercury occurs in deposits throughout the world mostly as cinnabar (mercuric sulfide). The red pigment vermilion is obtained by Mill (grinding), grinding natural cinnabar or synthetic mercuric sulfide. Mercury is used in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dynamo
file:DynamoElectricMachinesEndViewPartlySection USP284110.png, "Dynamo Electric Machine" (end view, partly section, ) A dynamo is an electrical generator that creates direct current using a commutator (electric), commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later Electric power conversion, electric-power conversion devices were based, including the electric motor, the Alternating current, alternating-current alternator, and the rotary converter. Today, the simpler alternator dominates large scale Electricity generation, power generation, for efficiency, reliability and cost reasons. A dynamo has the disadvantages of a commutator (electric), mechanical commutator. Also, converting alternating to direct current using rectifiers (such as vacuum tubes or more recently via Solid state (electronics), solid state technology) is effective and usually economical. History Induction with pe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alfvén Wave
In plasma physics, an Alfvén wave, named after Hannes Alfvén, is a type of plasma wave in which ions oscillate in response to a restoring force provided by an effective tension on the magnetic field lines. Definition An Alfvén wave is a low-frequency (compared to the ion gyrofrequency) travelling oscillation of the ions and magnetic field in a plasma. The ion mass density provides the inertia and the magnetic field line tension provides the restoring force. Alfvén waves propagate in the direction of the magnetic field, and the motion of the ions and the perturbation of the magnetic field are transverse to the direction of propagation. However, Alfvén waves existing at oblique incidences will smoothly change into magnetosonic waves when the propagation is perpendicular to the magnetic field. Alfvén waves are dispersionless. Alfvén velocity The low-frequency relative permittivity \varepsilon of a magnetized plasma is given by : \varepsilon = 1 + \frac where is the ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nobel Prize In Physics
) , image = Nobel Prize.png , alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then "MDCCCXXXIII" above, followed by (smaller) "OB•" then "MDCCCXCVI" below. , awarded_for = Outstanding contributions for humankind in the field of Physics , presenter = Royal Swedish Academy of Sciences , location = Stockholm, Sweden , date = , reward = 9 million Swedish kronor (2017) , year = 1901 , holder_label = Most recently awarded to , holder = Alain Aspect, John Clauser, and Anton Zeilinger , most_awards = John Bardeen (2) , website nobelprize.org, previous = 2021 , year2=2022, main=2022, next=2023 The Nobel Prize in Physics is a yearly award given by the Royal Swedish Academy of Sciences for those who have made the most outstanding contributions for humankind in the field of physics. It ... [...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] |
Magnetic Helicity
In plasma physics, magnetic helicity is a measure of the linkage, twist, and writhe of a magnetic field. In ideal magnetohydrodynamics, magnetic helicity is conserved. When a magnetic field contains magnetic helicity, it tends to form large-scale structures from small-scale ones. This process can be referred as an inverse transfer in Fourier space. This second property makes magnetic helicity special: three-dimensional turbulent flows tend to "destroy" structure, in the sense that large-scale vortices break-up in smaller and smaller ones (a process called "direct energy cascade", described by Lewis Fry Richardson and Andrey Nikolaevich Kolmogorov). At the smallest scales, the vortices are dissipated in heat through viscous effects. Through a sort of "inverse cascade of magnetic helicity", the opposite happens: small helical structures (with a non-zero magnetic helicity) lead to the formation of large-scale magnetic fields. This is for example visible in the heliospheric curren ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Field-reversed Configuration
A field-reversed configuration (FRC) is a type of plasma device studied as a means of producing nuclear fusion. It confines a plasma on closed magnetic field lines without a central penetration. In an FRC, the plasma has the form of a self-stable torus, similar to a smoke ring. FRCs are closely related to another self-stable magnetic confinement fusion device, the spheromak. Both are considered part of the compact toroid class of fusion devices. FRCs normally have a plasma that is more elongated than spheromaks, having the overall shape of a hollowed out sausage rather than the roughly spherical spheromak. FRCs were a major area of research in the 1960s and into the 1970s, but had problems scaling up into practical fusion triple products. Interest returned in the 1990s and , FRCs were an active research area. History The FRC was first observed in laboratories in the late 1950s during theta pinch experiments with a reversed background magnetic field. The first studies were a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
A Comparison Of An FRC And A Spheromak
A, or a, is the first letter and the first vowel of the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is ''a'' (pronounced ), plural ''aes''. It is similar in shape to the Ancient Greek letter alpha, from which it derives. The uppercase version consists of the two slanting sides of a triangle, crossed in the middle by a horizontal bar. The lowercase version can be written in two forms: the double-storey a and single-storey ɑ. The latter is commonly used in handwriting and fonts based on it, especially fonts intended to be read by children, and is also found in italic type. In English grammar, " a", and its variant " an", are indefinite articles. History The earliest certain ancestor of "A" is aleph (also written 'aleph), the first letter of the Phoenician alphabet, which consisted entirely of consonants (for that reason, it is also called an abjad to distinguish it f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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