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Swedish physicist Hannes Alfvén won the Nobel Prize in physics in 1970. Alfvén worked in magnetohydrodynamics (the study of plasmas in magnetic fields) and founded the field of plasma physics.

Hannes Olof Gösta Alfvén (1908-1995), Swedish physicist and Nobel laureate. For his discoveries in the field of plasma physics—the study of gaslike mixtures consisting of electrically charged particles (see Elementary Particles) found primarily in outer space—Alfvén was awarded the 1970 Nobel Prize for physics, which he shared with French physicist Louis Néel. Researchers have applied Alfvén's ideas to the study of sunspots, cosmic rays, and the origin of galaxies and the solar system. His work also has helped researchers develop thermonuclear reactors, devices that produce nuclear power (see Nuclear Energy).

Born in Norrköping, Sweden, Alfvén attended the University of Uppsala in Sweden, receiving a Ph.D. degree in 1934. Soon after graduating, he accepted a professorship at the University of Uppsala, where he remained until 1937. He went on to serve as a researcher at the Nobel Institute of Physics in Stockholm, Sweden, until 1940. After teaching abroad for several years, Alfvén became a professor at the Royal Institute of Technology in Stockholm. In 1967 he moved to the United States to teach at the University of California at San Diego.

Alfvén's research in plasma physics made him one of the founders of the field. He showed that a plasma has an electric current (a flow of charged particles) that produces a magnetic field (see Magnetism). He also showed that, under certain conditions, the plasma binds, or freezes, the magnetic field, meaning that the plasma and the magnetic field move together. Physicists call this the frozen-in-flux theorem.

In 1939 Alfvén published a theory relating magnetic storms to the aurora. Magnetic storms occur when plasma streams from the sun enter the earth's upper atmosphere. The collisions between the energetic charged particles of the incoming plasma and the neutral gas molecules in the atmosphere release energy that is then seen as the light in the aurora. The aurora—commonly referred to as the aurora borealis (northern lights) or the aurora australis (southern lights) according to its location—occurs in high latitudes of both of the earth's hemispheres and consists of immense, rapidly shifting curtains and columns of pastel-colored lights. In his theory, Alfvén introduced a mathematical approximation that physicists now widely use to calculate the complex motion of a charged particle in a magnetic field.

Alfvén's work on the motion of electrically conducting fluids in a magnetic field was concerned primarily with geophysics and astrophysics. His research led him to postulate “Alfvén's waves,” transverse electromagnetic waves (see Electromagnetic Radiation) transmitted by plasma. Scientists later confirmed the waves in plasmas and liquid metals.