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Alfvén Mach number

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In plasma physics, the Alfvén Mach number (also known as the Alfvén number, Alfvénic Mach number, and magnetic Mach number; MA or MM) is a dimensionless quantity representing the ratio of the relative velocity of a fluid to the local Alfvén speed. Along with the sonic Mach number, the Alfvén Mach number is frequently used to characterize shock fronts and turbulence in magnetized plasmas. M A = u u A {\displaystyle \mathrm {M_{A}} ={\frac {u}{u_{\mathrm {A} }}}} where

  • MA is the Alfvén Mach number,
  • u is the flow velocity, and
  • uA is the Alfvén speed.

When u < MA, the flow is referred to as sub-Alfvénic; and when u > MA, the flow is referred to as super-Alfvénic.

See also

References

  1. Droege, W.; Schlickeiser, R. (1986). "Particle Acceleration in Solar Flares". The Astrophysical Journal. 305: 909. Bibcode:1986ApJ...305..909D. doi:10.1086/164305.
  2. ^ Treumann, R. A. (2009). "Fundamentals of Collisionless Shocks for Astrophysical Application, 1. Non-Relativistic Shocks". The Astronomy and Astrophysics Review. 17 (4): 409–535. Bibcode:2009A&ARv..17..409T. doi:10.1007/s00159-009-0024-2.
  3. Kang, Hyesung; Ryu, Dongsu (2013). "DIFFUSIVE SHOCK ACCELERATION AT COSMOLOGICAL SHOCK WAVES". The Astrophysical Journal. 764 (1): 95. arXiv:1212.3246. Bibcode:2013ApJ...764...95K. doi:10.1088/0004-637X/764/1/95.
  4. Cho, Jungyeon; Lazarian, A. (October 2003). "Compressible Magnetohydrodynamic Turbulence: Mode Coupling, Scaling Relations, Anisotropy, Viscosity-Damped Regime and Astrophysical Implications". Monthly Notices of the Royal Astronomical Society. 345 (1): 325–339. Bibcode:2003MNRAS.345..325C. doi:10.1046/j.1365-8711.2003.06941.x.
  5. Padoan, Paolo; Jimenez, Raul; Juvela, Mika; Nordlund, Åke (2004). "The Average Magnetic Field Strength in Molecular Clouds: New Evidence of Super-Alfvénic Turbulence". The Astrophysical Journal. 604 (1): L49 – L52. arXiv:astro-ph/0311349. Bibcode:2004ApJ...604L..49P. doi:10.1086/383308.
  6. De Keyser, Johan; Roth, Michel; De Sterck, Hans; Poedts, Stefaan (2001). "A Survey of Field-Aligned Mach Number and Plasma Beta in the Solar Wind". The 3-D Heliosphere at Solar Maximum: 201–204. Bibcode:2001SSRv...97..201D. doi:10.1007/978-94-017-3230-7_31.
  7. Tofflemire, Benjamin M.; Burkhart, Blakesley; Lazarian, A. (2011). "INTERSTELLAR SONIC AND ALFVÉNIC MACH NUMBERS AND THE TSALLIS DISTRIBUTION". The Astrophysical Journal. 736 (1): 60. arXiv:1103.3299. Bibcode:2011ApJ...736...60T. doi:10.1088/0004-637X/736/1/60.
  8. Beresnyak, A. (October 2023). 2023 NRL Plasma Formulary. Washington, DC: Naval Research Laboratory.
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