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| [[Image:Magnetic rope.svg|thumb|300px|The complex self-constricting magnetic field lines and current paths in a [[Birkeland current]] that may develop in a plasma (''[http://history.nasa.gov/SP-345/ch15.htm#250 Evolution of the Solar System]'', 1976) ]]
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| '''Plasma parameters''' define various characteristics of a [[Plasma (physics)|plasma]], an electrically conductive collection of [[charged particle]]s that responds ''collectively'' to [[electromagnetic force]]s. Plasma typically takes the form of neutral gas-like clouds or charged [[ion beam]]s, but may also include dust and grains. <ref>Peratt, Anthony, ''Physics of the Plasma Universe'' (1992); </ref> The behaviour of such particle systems can be studied statistically. <ref>Parks, George K., Physics of Space Plasmas (2004, 2nd Ed.)</ref>
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| == Fundamental plasma parameters ==
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| All quantities are in [[Gaussian units|Gaussian]] ([[Centimetre-gram-second system of units|cgs]]) units except [[temperature]] expressed in eV and ion mass expressed in units of the [[proton]] mass <math>\mu = m_i/m_p</math>; ''Z'' is charge state; ''k'' is [[Boltzmann's constant]]; ''K'' is wavenumber; γ is the [[adiabatic index]]; ln Λ is the [[Coulomb logarithm]].
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| === Frequencies ===
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| *'''electron gyrofrequency''', the angular frequency of the circular motion of an electron in the plane perpendicular to the magnetic field:
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| :<math>\omega_{ce} = eB/m_ec = 1.76 \times 10^7 B \mbox{rad/s} \,</math>
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| *'''ion gyrofrequency''', the angular frequency of the circular motion of an ion in the plane perpendicular to the magnetic field:
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| :<math>\omega_{ci} = eB/m_ic = 9.58 \times 10^3 Z \mu^{-1} B \mbox{rad/s} \,</math>
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| *'''electron plasma frequency''', the frequency with which electrons oscillate ([[plasma oscillation]]):
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| :<math>\omega_{pe} = (4\pi n_ee^2/m_e)^{1/2} = 5.64 \times 10^4 n_e^{1/2} \mbox{rad/s}</math>
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| *'''ion plasma frequency''':
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| :<math>\omega_{pi} = (4\pi n_iZ^2e^2/m_i)^{1/2} = 1.32 \times 10^3 Z \mu^{-1/2} n_i^{1/2} \mbox{rad/s}</math>
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| *'''electron trapping rate''':
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| :<math>\nu_{Te} = (eKE/m_e)^{1/2} = 7.26 \times 10^8 K^{1/2} E^{1/2} \mbox{s}^{-1} \,</math>
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| *'''ion trapping rate''':
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| :<math>\nu_{Ti} = (ZeKE/m_i)^{1/2} = 1.69 \times 10^7 Z^{1/2} K^{1/2} E^{1/2} \mu^{-1/2} \mbox{s}^{-1} \,</math>
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| *'''electron collision rate''':
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| :<math>\nu_e = 2.91 \times 10^{-6} n_e\,\ln\Lambda\,T_e^{-3/2} \mbox{s}^{-1}</math>
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| *'''ion collision rate''':
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| :<math>\nu_i = 4.80 \times 10^{-8} Z^4 \mu^{-1/2} n_i\,\ln\Lambda\,T_i^{-3/2} \mbox{s}^{-1}</math>
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| === Lengths ===
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| *'''[[Thermal de Broglie wavelength|Electron thermal de Broglie wavelength]]''', approximate average [[de Broglie wavelength]] of electrons in a plasma:
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| :<math>\Lambda_e= \sqrt{\frac{h^2}{2\pi m_ekT_e}}= 6.919\times 10^{-8}\,T_e^{-1/2}\,\mbox{cm}</math>
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| *'''classical distance of closest approach''', the closest that two particles with the elementary charge come to each other if they approach head-on and each have a velocity typical of the temperature, ignoring quantum-mechanical effects:
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| :<math>e^2/kT=1.44\times10^{-7}\,T^{-1}\,\mbox{cm}</math>
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| *'''electron gyroradius''', the radius of the circular motion of an electron in the plane perpendicular to the magnetic field:
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| :<math>r_e = v_{Te}/\omega_{ce} = 2.38\,T_e^{1/2}B^{-1}\,\mbox{cm}</math>
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| *'''ion gyroradius''', the radius of the circular motion of an ion in the plane perpendicular to the magnetic field:
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| :<math>r_i = v_{Ti}/\omega_{ci} = 1.02\times10^2\,\mu^{1/2}Z^{-1}T_i^{1/2}B^{-1}\,\mbox{cm}</math>
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| *'''plasma [[skin depth]]''', the depth in a plasma to which electromagnetic radiation can penetrate:
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| :<math>c/\omega_{pe} = 5.31\times10^5\,n_e^{-1/2}\,\mbox{cm}</math>
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| *'''[[Debye length]]''', the scale over which electric fields are screened out by a redistribution of the electrons:
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| :<math>\lambda_D = (kT/4\pi ne^2)^{1/2} = 7.43\times10^2\,T^{1/2}n^{-1/2}\,\mbox{cm}</math>
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| *'''[[Ion inertial length]]''', the scale at which ions decouple from electrons and the magnetic field becomes frozen into the electron fluid rather than the bulk plasma:
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| :<math>d_i = c/\omega_{pi}</math>
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| === Velocities ===
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| *'''electron thermal velocity''', typical velocity of an electron in a [[Maxwell-Boltzmann distribution]]:
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| :<math>v_{Te} = (kT_e/m_e)^{1/2} = 4.19\times10^7\,T_e^{1/2}\,\mbox{cm/s}</math>
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| *'''ion thermal velocity''', typical velocity of an ion in a [[Maxwell-Boltzmann distribution]]:
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| :<math>v_{Ti} = (kT_i/m_i)^{1/2} = 9.79\times10^5\,\mu^{-1/2}T_i^{1/2}\,\mbox{cm/s}</math>
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| *'''ion sound velocity''', the speed of the longitudinal waves resulting from the mass of the ions and the pressure of the electrons:
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| :<math>c_s = (\gamma ZkT_e/m_i)^{1/2} = 9.79\times10^5\,(\gamma ZT_e/\mu)^{1/2}\,\mbox{cm/s}</math>
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| *'''[[Hannes Alfvén|Alfvén]] velocity''', the speed of the [[Alfvén wave|waves]] resulting from the mass of the ions and the restoring force of the magnetic field:
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| :<math>v_A = B/(4\pi n_im_i)^{1/2} = 2.18\times10^{11}\,\mu^{-1/2}n_i^{-1/2}B\,\mbox{cm/s}</math>
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| === Dimensionless ===
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| [[Image:fusor_running.jpg|thumb|right|300px|A 'sun in a test tube'. The [[Farnsworth-Hirsch Fusor]] during operation in so called "star mode" characterized by "rays" of glowing plasma which appear to emanate from the gaps in the inner grid.]]
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| *square root of electron/proton mass ratio
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| :<math>(m_e/m_p)^{1/2} = 2.33\times10^{-2} = 1/42.9 \,</math>
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| * number of particles in a Debye sphere
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| :<math>(4\pi/3)n\lambda_D^3 = 1.72\times10^9\,T^{3/2}n^{-1/2}</math>
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| * Alfvén velocity/speed of light
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| :<math>v_A/c = 7.28\,\mu^{-1/2}n_i^{-1/2}B</math>
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| * electron plasma/gyrofrequency ratio
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| :<math>\omega_{pe}/\omega_{ce} = 3.21\times10^{-3}\,n_e^{1/2}B^{-1}</math>
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| * ion plasma/gyrofrequency ratio
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| :<math>\omega_{pi}/\omega_{ci} = 0.137\,\mu^{1/2}n_i^{1/2}B^{-1}</math>
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| * thermal/magnetic pressure ratio ("[[Beta (plasma physics)|beta]]")
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| :<math>\beta = 8\pi nkT/B^2 = 4.03\times10^{-11}\,nTB^{-2}</math>
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| * magnetic/ion rest energy ratio
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| :<math>B^2/8\pi n_im_ic^2 = 26.5\,\mu^{-1}n_i^{-1}B^2</math>
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| ==See also==
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| *[[List of plasma (physics) articles]]
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| ==References==
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| * [http://www.ipp.mpg.de/~dpc/nrl/ NRL Plasma Formulary] (esp. [http://www.ipp.mpg.de/~dpc/nrl/28.html p. 28] and [http://www.ipp.mpg.de/~dpc/nrl/29.html p. 29]), J.D. Huba, [[United States Naval Research Laboratory|Naval Research Laboratory]] (2007)
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| ==Footnotes==
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| <div style="font-size: 95%">
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| <!--See [[Wikipedia:Footnotes]] for an explanation of how to generate footnotes using the <ref(erences/)> tags-->
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| <references/>
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| </div>
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| <!--Categories-->
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| [[Category:Plasma physics| ]]
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| [[Category:Plasma diagnostics]]
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| [[Category:Astrophysics]]
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Hello, my name is Andrew and my spouse doesn't like it at all. Distributing production has been his profession for some time. As a lady what she really likes is style and she's been performing it for fairly a while. My wife and I reside in Kentucky.
Here is my blog psychic readers (http://www.youronlinepublishers.com/)