Magnetohydrodynamics (MHD) (magnetofluiddynamics or hydromagnetics), is the academic discipline which studies the dynamics of electrically conducting fluids. Examples of such fluids include plasmas, liquid metals, and salt water.

The set of equations which describe MHD are a combination of the Navier-Stokes equations of fluid dynamics and Maxwell's equations of electromagnetism. These differential equations have to be solved simultaneously. This is too complex or impossible to do symbolically in all but the most trivial cases. For real-world problems, numeric solutions are found using supercomputers.

The fluid mantle of the Earth is theorized to be a huge MHD dynamo that generates the Earth's magnetic field due to the motion of the molten rock. Similarly, the magnetic fields of some planets and all stars are believed to be caused by fluid motion.

Because stars are rotating magnetic balls of plasma, much of their activity is governed by MHD. Sunspots are caused by the Sun's magnetic fields, as Joseph Larmor theorized in 1919, as is the differential solar rotation.

Applications

MHD is related to engineering problems such as plasma confinement, liquid-metal cooling of nuclear reactors, and electromagnetic casting (among others). Electromagnetic interactions with fluids and plasmas is especially important to physicists in the study of stellar fusion and the solar wind. It also finds applications in some areas of geophysics.

In early 1990s, Mitsubishi built a boat, the 'Yamoto', which uses a magnetohydrodynamic drive, is driven by a liquid helium-cooled superconductor, and can travel at 15 km/h.

See also

• Alfvén wave
• Electromagnetic casting
• Ferrofluid
• Magnetic reconnection
• MHD generator
• Magnetohydrodynamic drive
• Nuclear reactor liquid-metal cooling
• Plasma equilibria and stability- plasma confinement
• Tokamak

References

• P. A. Davidson, "An Introduction to Magnetohydrodynamics", May 2001 452 p ISBN 0521794870
• Jordan, R.,"A statistical equilibrium model of coherent structures in magnetohydrodynamics". Nonlinearity 8 (July 1995) 585-613.
• Hurricane, O. A., B. H. Fong, and S. C. Cowley, "Nonlinear magnetohydrodynamic detonation: Part I". Physics of Plasmas Vol 4(10) pp. 3565-3580. October 1997.
• Tabar, M. R. Rahimi, and S. Rouhani, "Turbulent Two Dimensional Magnetohydrodynamics and Conformal Field Theory". Department of Physics, Sharif University of Technology. Institute for Studies in Theoretical Physics and Mathematics. Tehran, Iran. arXiv:hep-th/9503005 v1 1 Mar 1995.
• Pai, Shih-I. "Magnetogasdynamics and Plasma Dynamics". Vienna: Springer-Verlag, 1962. 197 p. ASIN 0387806083
• Biskamp, Dieter. "Nonlinear Magnetohydrodynamics". Cambridge, England: Cambridge University Press, 1993. 378 p. ISBN 0521599180
• Ferraro, Vincenzo Consolato Antonio and Plumpton, Charles. "An Introduction to Magneto-Fluid Mechanics", 2nd ed.
• Roberts, P.H. "Introduction to Magnetohydrodynamics". London: Longmans Green, 1967.
• Kulikovskiy, A.G. & Lyubimov, G.A. "1965 Magnetohydrodynamics". Addison&Wesley, Massachusetts.
• Sutton, G. W., and A. Sherman, "Engineering Magnetohydrodynamics", McGraw-Hill Book Company, New York, 1965.
• "Magnetohydrodynamic Generators with Nonequilibrium Ionization", AIAA Journal, Vol. 3, April, 1965, p 591.
• Hughes, W., and F. Young, "The Electromagnetodynamics of Fluids", New York, John Wiley & Sons Inc. 1966.
• Dr. James B. Calvert, "Magnetohydrodynamics", 2002-10-20
• David P. Stern, NASA, "The Sun's Magnetic Cycle"