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Two-stream Instability
The two-stream instability is a very common instability in plasma physics. It can be induced by an energetic particle stream injected in a plasma, or setting a current along the plasma so different species (ions and electrons) can have different drift velocities. The energy from the particles can lead to plasma wave excitation. Two-stream instability can arise from the case of two cold beams, in which no particles are resonant with the wave, or from two hot beams, in which there exist particles from one or both beams which are resonant with the wave. Two-stream instability is known in various limiting cases as beam-plasma instability, beam instability, or bump-on-tail instability. Dispersion relation in cold-beam limit Consider a cold, uniform, and unmagnetized plasma, where ions are stationary and the electrons have velocity v_0, that is, the reference frame is moving with the ion stream. Let the electrostatic waves be of the form: \mathbf_1 = \xi_1 \exp (kx - \omega t)\ ... [...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] |
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] |
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 wavele ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plasma Wave
In plasma physics, waves in plasmas are an interconnected set of particles and fields which propagate in a periodically repeating fashion. A plasma is a quasineutral, electrically conductive fluid. In the simplest case, it is composed of electrons and a single species of positive ions, but it may also contain multiple ion species including negative ions as well as neutral particles. Due to its electrical conductivity, a plasma couples to electric and magnetic fields. This complex of particles and fields supports a wide variety of wave phenomena. The electromagnetic fields in a plasma are assumed to have two parts, one static/equilibrium part and one oscillating/perturbation part. Waves in plasmas can be classified as electromagnetic or electrostatic according to whether or not there is an oscillating magnetic field. Applying Faraday's law of induction to plane waves, we find \mathbf\times\tilde=\omega\tilde, implying that an electrostatic wave must be purely longitudinal. An el ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bump On Tail Dist
Bump or Bumps may refer to: * A collision or impact * A raised protrusion on the skin such as a pimple, goose bump, prayer bump, lie bumps, etc. Infrastructure and industry * Coal mine bump, a seismic jolt occurring within a mine * Bump (union), in a unionised work environment, a reassignment of jobs on the basis of seniority * Bumper music or bump, in radio broadcasting a short clip of music used for transitions between program elements * Bump, airline travel slang for the involuntary denial of boarding to passengers on an overbooked flight Arts and entertainment * Bump (dance), a dance from the 1970s disco era * ''BUMP'' (comics), 2007-8 limited edition comic book series Music * "The Bump", a funky song by the Commodores from ''Machine Gun''(1974) * "The Bump", a 1974 hit single by the band Kenny * ''Bump'' (album), a jazz album recorded by musician John Scofield in 2000 * "Bump", a song by Raven-Symoné from '' This Is My Time'' * "Bump", a song by Fun Lovin' Criminals ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Landau Damping
In physics, Landau damping, named after its discoverer,Landau, L. "On the vibration of the electronic plasma". ''JETP'' 16 (1946), 574. English translation in ''J. Phys. (USSR)'' 10 (1946), 25. Reproduced in Collected papers of L.D. Landau, edited and with an introduction by D. ter Haar, Pergamon Press, 1965, pp. 445–460; and in Men of Physics: L.D. Landau, Vol. 2, Pergamon Press, D. ter Haar, ed. (1965). Soviet physicist Lev Davidovich Landau (1908–68), is the effect of damping ( exponential decrease as a function of time) of longitudinal space charge waves in plasma or a similar environment.Chen, Francis F. ''Introduction to Plasma Physics and Controlled Fusion''. Second Ed., 1984 Plenum Press, New York. This phenomenon prevents an instability from developing, and creates a region of stability in the parameter space. It was later argued by Donald Lynden-Bell that a similar phenomenon was occurring in galactic dynamics, where the gas of electrons interacting by electrostatic for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
