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== Other ==
All quantities are in [[Gaussian units|Gaussian]] ([[Centimetre-gram-second system of units|cgs]]) units except [[energy]] <math>E</math> and [[temperature]] <math>T</math> which are in [[electronvolt]]s. For the sake of simplicity, a single ionic species is assumed. The ion mass is expressed in units of the [[proton]] mass, <math>\mu = m_i/m_p</math> and the ion charge in units of the [[elementary charge]] {{nowrap|<math>e</math>,}} <math>Z = q_i/e</math> (in the case of a fully ionized atom, <math>Z</math> equals to the respective [[atomic number]]). The other physical quantities used are the [[Boltzmann constant]] {{nowrap|(<math>
=== Frequencies ===
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{{unordered list
| '''[[Thermal de Broglie wavelength|electron thermal de Broglie wavelength]]''', approximate average [[de Broglie wavelength]] of electrons in a plasma:
<math display="block">\lambda_{\mathrm{th},e} = \sqrt{\frac{h^2}{2\pi m_e
| '''classical distance of closest approach''', also known as "Landau length" the closest that two particles with the elementary charge come to each other if they approach head-on and each has a velocity typical of the temperature, ignoring quantum-mechanical effects:
<math display="block">\frac{e^2}{
| '''electron gyroradius''', the radius of the circular motion of an electron in the plane perpendicular to the magnetic field:
<math display="block">r_e = \frac{v_{Te}}{\omega_{ce}} \approx 2.38\,\frac{{T_e}^\frac{1}{2}}{B}\ \mbox{cm}</math>
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<math display="block">\frac{c}{\omega_{pe}} \approx 5.31 \times 10^5\,\frac{1}{{n_e}^\frac{1}{2}}\ \mbox{cm}</math>
| '''[[Debye length]]''', the scale over which electric fields are screened out by a redistribution of the electrons:
<math display="block">\lambda_D = \left(\frac{
| '''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:
<math display="block">d_i = \frac{c}{\omega_{pi}} \approx 2.28 \times 10^7\, \frac{1}{Z} \left(\frac{\mu}{n_i}\right)^\frac{1}{2}\ \mbox{cm}</math>
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{{unordered list
| '''electron thermal velocity''', typical velocity of an electron in a [[Maxwell–Boltzmann distribution]]:
<math display="block">v_{Te} = \left(\frac{
| '''ion thermal velocity''', typical velocity of an ion in a [[Maxwell–Boltzmann distribution]]:
<math display="block">v_{Ti} = \left(\frac{
| '''ion speed of sound''', the speed of the longitudinal waves resulting from the mass of the ions and the pressure of the electrons:
<math display="block">c_s = \left(\frac{\gamma
where <math>\gamma</math> is the [[adiabatic index]]
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=== Dimensionless ===
* number of particles in a Debye sphere <math display="block">
* Alfvén speed to speed of light ratio <math display="block">\frac{v_A}{c} \approx 7.28\,\frac{B}{\left(\mu n_i\right)^\frac{1}{2}}</math>
* electron plasma frequency to gyrofrequency ratio <math display="block">\frac{\omega_{pe}}{\omega_{ce}} \approx 3.21 \times 10^{-3}\,\frac{{n_e}^\frac{1}{2}}{B}</math>
* ion plasma frequency to gyrofrequency ratio <math display="block">\frac{\omega_{pi}}{\omega_{ci}} \approx 0.137\,\frac{\left(\mu n_i\right)^\frac{1}{2}}{B}</math>
* thermal pressure to magnetic pressure ratio, or [[beta (plasma physics)|beta]], ''β'' <math display="block">\beta = \frac{8\pi
* [[magnetic energy|magnetic field energy]] to [[invariant mass#Rest energy|ion rest energy]] ratio <math display="block">\frac{B^2}{8\pi n_i m_i c^2} \approx 26.5\,\frac{B^2}{\mu n_i}</math>
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The [[Plasma (physics)|plasma]] collisionality <math>\nu^*</math> is defined as<ref>{{ cite journal | author1 = ITER Physics Expert Group on Diagnostics | author2 = ITER Physics Basis | date = 1999 | title = Chapter 7: Measurement of plasma parameters | url = https://iopscience.iop.org/article/10.1088/0029-5515/39/12/307 | journal = Nuclear Fusion | volume = 39 | issue = 12 | pages = 2541–2575 | doi = 10.1088/0029-5515/39/12/307 | issn = 0029-5515 }}</ref><ref>{{ cite journal | last1 = Wenzel | first1 = K.W. | last2 = Sigmar | first2 = D.J. | date = 1990-06-01 | title = Neoclassical analysis of impurity transport following transition to improved particle confinement | url = https://iopscience.iop.org/article/10.1088/0029-5515/30/6/013 | journal = Nuclear Fusion | volume = 30 | issue = 6 |pages = 1117–1127 | doi = 10.1088/0029-5515/30/6/013 | issn = 0029-5515 }}</ref>
<math display="block">
\nu^* = \nu_\mathrm{ei} \, \sqrt{\frac{m_\mathrm{e}}{k_\mathrm{B} T_\mathrm{e}}} \, \
</math>
where <math>\nu_\mathrm{ei}</math> denotes the electron-ion [[collision frequency]], <math>R</math> is the major radius of the plasma, <math>\
==Electron temperature==
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