Magnetohydrodynamics is the scientific discipline which studies the dynamics of electrically conducting fluids, which include liquid metals, plasmas, and salt water. The field of magnetohydrodynamics was started by Hannes Alfvén, who was awarded the Nobel Prize in Physics in 1970.
The idea of magnetohydrodynamics is that magnetic fields can induce currents in a moving conductive fluid, creating forces on the fluid, and changing the magnetic field itself. The set of equations which describe magnetohydrodynamics are a combination of the Navier-Stokes equations of fluid dynamics and Maxwell's equations of electromagnetism. These differential equations must to be solved simultaneously, either analytically or numerically.