- The study of the interactions between an electrically conducting fluid and magnetic fields. Plasmas, liquid metals, and ionized gases are examples of such fluids. Hydromagnetics has applications in various fields, including plasma confinement, liquid-metal cooling of nuclear reactors, and in astronomy. Also called magnetohydrodynamics, or magneto-fluid dynamics. When dealing specifically with electrically conducting gases, also called magnetogasdynamics, and when dealing with plasmas, also called magnetoplasmadynamics.