Alfvén, Hannes Olof Gösta (1908-1995) was a Swedish theoretical physicist who shared the Nobel Prize in physics in 1970 for his study of the ways in which electric and magnetic fields interact with fluids that conduct electiicity. Alfvén's work influenced the study and exploration of space as well as the design of nuclear fusion reactors, devices in which controlled nuclear reactions take place.

Alfvén was born in 1908 in Norrköping, Sweden, to Johannes and Anna-Clara (Romanus) Alfvén. Johannes and Anna-Clara both worked as physicians. Alfvén received his early education in Nörrkoping and earned a Ph.D. degree in physics from the University of Uppsala in 1934. He remained at the university as a lecturer in physics until 1937, when he became a research physicist at the Nobel Institute for Physics in Stockholm. He joined the faculty of the Royal Institute of Technology in Stockholm in 1940, becoming professor of electronics in 1945 and professor of plasma physics in 1963. Plasma physics concerns the study of gases called plasmas, which result when enough energy is introduced into a gas and the gas becomes ionized (separated into positively and negatively charged particles). Plasma makes up more than 99 percent of all matter in the universe.

In 1967, Alfvén accepted a position as professor of applied physics at the University of California, San Diego. He left Sweden due partly to conflicts he had with the government over issues ranging from education policy to nuclear reactor design.

Throughout his academic career, Alfvén performed pioneering research work on plasmas and how they behaved in magnetic and electric fields. In his early work, Alfvén explored the nature of sunspots and the aurora borealis. Sunspots are areas on the surface of the sun that appear dark because they are cooler than the rest of the sun's visible surface. Auroras create the most visible effect of the sun's activity on the earth's atmosphere. The stream of gas flowing from the sun— the solar wind—is composed of plasmas. When these particles enter the earth's magnetic field, they move toward the poles, creating the auroral display. In the Northern Hemisphere, this display of light in the night sky is called the aurora borealis, or the northern lights. In the Southern Hemisphere, it is called the aurora australis.

Although his ideas initially were rejected, Alfvén made many significant predictions about how plasmas would behave, based on his work. He showed that a plasma is associated with a magnetic field related to the flow of charged particles (electric currents) in the plasma, and that under certain conditions the magnetic field could become “frozen” in the plasma. This meant that if such a plasma moves, the magnetic field moves with it.

Alfvén also made a great contribution to the understanding of the earth's magnetic field. He introduced the idea of circular rotation about a “guiding center.” That center, he proposed, drifts along magnetic field lines. Applying this principle to the study of magnetic storms and auroras, Alfvén said that particles in the earth's magnetic field should bounce back and forth along the field lines. Scientists later applied Alfvén's ideas to interpreting such phenomena as the Van Allen belts, also called radiation belts, two zones of electrically charged particles that surround the earth high above its surface. The belts surround the earth somewhat like doughnuts. Another of Alfvén's early suggestions that proved valid was the existence of weak magnetic fields throughout the galaxy due to the presence of even small amounts of plasma.

Alfvén made one of his strongest predictions in 1942, when he predicted the existence of waves in plasmas. Alfvén predicted that magnetic field lines in a plasma behaved as stretched rubber