magnetohydrodynamics

magnetohydrodynamics , study of the motions of electrically conducting fluids and their interactions with magnetic fields. The principles of magnetohydrodynamics are of particular importance in plasma physics. See nuclear energy .

magnetohydrodynamics The science of relating magnetic fields, mainly mathematically, within a moving conducting medium. It is mainly applicable to the Earth's core, where the geomagnetic field is generated by the motion of magnetic lines of force that are ‘frozen’ within a moving, electrically conducting medium, but it is also applicable to all systems involving the fluid motion of electrically conducting materials within a magnetic field.

magnetohydrodynamics (MHD) The study of the interactions between a plasma (ionized gas) and a magnetic field. Plasma, being ionized, is a good electrical conductor. An electric current is induced in a plasma when it tries to cross lines of magnetic force, and the plasma then tends to follow the magnetic field lines. The magnetic field is said to be ‘frozen in’ to the plasma, or vice versa. Depending on the relative energies in the plasma and the magnetic field, the plasma may be forced to move only along the magnetic field lines, as in a quiescent solar prominence, or the magnetic field lines may be dragged along by the motion of the plasma, as in the Earth's magnetosphere and magnetotail. Waves propagating in a plasma frozen into a magnetic field are called Alfvén waves.