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Nobel Laureate Hannes Alfvén passed away on April 2, 1995, at his home in Djursholm, Sweden. His vigorous scientific activity lasted for six decades and led to remarkable achievements in a number of areas of plasma physics, space physics and astrophysics. He was awarded the 1970 Nobel Prize for Physics "for his contributions and fundamental discoveries in magneto-hydrodynamics and their fruitful applications in different areas of plasma physics", and remained scientifically active well beyond his 80th birthday. In addition to the Nobel Prize, Hannes Alfvén received many other honours, including the Gold Medal of the Royal Astronomical Society (1967). He was one of the few who were members of both the American and the Soviet Academies of Science.
Hannes Alfvén was born on May 30, 1908, in Norrköping, Sweden. His lifelong interest in astronomy and astrophysics was kindled when, during his school years, he passionately read a book on Popular Astronomy by Camille Flammarion. Also of great importance in his intellectual development and his scientific career was his interest in electronics, based on his activity in the school's radio club. In retrospect, it is clear that an important key to his success was the fresh perspective he gained by approaching astrophysical problems from an electromagnetic point of view.
His rapid academic career led to a doctorate at the age of 24 and a full professorship at the Royal Institute of Technology in Stockholm at the age of 32. As a professor, he was an exceptionally inspiring and generous leader, spreading fruitful ideas around him without any claim to co-authorship of publications deriving from them. His vigorous scientific activity led to the creation of several new professorships and departments, three of which now form a separate entity within the Royal Institute of Technology, the Alfvén Laboratory.
From 1967 to 1988, Hannes Alfvén held a professorship at the University of California, San Diego, but remained in close contact with his friends and colleagues at the Royal Institute of Technology, where he spent the time "from the vernal equinox until the autumnal equinox." His annual return was always something to look forward to.
Already in his mid-twenties, Hannes Alfvén attempted to develop a theory of the origin of cosmic radiation. His paper on this in Nature (1933) and all of his later work is permeated by the principle that theories of cosmical phenomena must agree with known results from laboratory experiments on Earth, because the same laws of nature must apply everywhere.
In considering the cosmic ray problem, he proposed (in 1937) that there exists a galactic magnetic field, but this proposal was generally dismissed. It was later recognized that the galactic magnetic field exists, but apparently without recognition of Hannes Alfvén's original proposal.
His most well-known discovery, of what we now call Alfvén waves, opened a whole new field of research, that of magnetohydrodynamics, which has become an indispensable tool in plasma physics and its applications, not least in astrophysics. It combined electromagnetic theory and fluid dynamics, which until then had been well established but as separate entities. Acceptance of the discovery was slow, and some critics maintained that if the waves described by Alfvén existed, Maxwell would have discovered them. But when, in 1948, Enrico Fermi acknowledged the existence of the new waves, the entire physics community was quick to concur.
Another fundamental contribution by Alfvén is the guiding centre approximation for the motion of charged particles, which has become another invaluable tool throughout the field of plasma physics and much used in cosmical physics
One of his most daring ideas was that of critical velocity in plasma neutral-gas interaction. Introduced as an assumption in a theory of the origin of planets around the sun and satellites around planets, it implies that neutral atoms moving relatively to a collisionless plasma would suddenly become ionized, and their relative motion would brake, at a certain critical velocity. The assumption was in contradiction with contemporary notions in plasma physics, but has later been confirmed experimentally in the laboratory as well as in space.
Some of Hannes Alfvén's ideas are still unaccepted or controversial. Examples are the concept of partial corotation (at a velocity equal to of the Kepler velocity), which he introduced to explain the structure of the Saturnian ring system (and to successfully predict that Uranus would prove to have a ring system). Another example is symmetric cosmology, which implies that the universe as a whole may consist of equal amounts of plasma and antiplasma, separated by thin boundary layers (producing unobservably small annihilation radiation).
Hannes Alfvén and his wife Kerstin took an active interest in global issues such as the environment, population growth, and disarmament. During a period of several years in the 1970s, Hannes Alfvén was President of the Pugwash movement, which, initiated by Albert Einstein and Bertrand Russell, annually gathered eminent scientists from all over the world to discuss such issues. Originally an advocate for the peaceful use of nuclear energy, he became a vigorous opponent when he realized its problems and connections with nuclear arms.
Hannes Alfvén's contribution to the progress of science is not limited to his own work but also includes the extraordinary inspiration that he has given to his many students as well as to colleagues all over the world. I am myself deeply grateful for his immensely valuable inspiration, guidance, and deep personal friendship throughout decades of wonderful collaboration.
Carl-Gunne Fälthammar
Hannes Alfvén was born on May 30, 1908, in Norrköping, Sweden. His lifelong interest in astronomy and astrophysics was kindled when, during his school years, he passionately read a book on Popular Astronomy by Camille Flammarion. Also of great importance in his intellectual development and his scientific career was his interest in electronics, based on his activity in the school's radio club. In retrospect, it is clear that an important key to his success was the fresh perspective he gained by approaching astrophysical problems from an electromagnetic point of view.
His rapid academic career led to a doctorate at the age of 24 and a full professorship at the Royal Institute of Technology in Stockholm at the age of 32. As a professor, he was an exceptionally inspiring and generous leader, spreading fruitful ideas around him without any claim to co-authorship of publications deriving from them. His vigorous scientific activity led to the creation of several new professorships and departments, three of which now form a separate entity within the Royal Institute of Technology, the Alfvén Laboratory.
From 1967 to 1988, Hannes Alfvén held a professorship at the University of California, San Diego, but remained in close contact with his friends and colleagues at the Royal Institute of Technology, where he spent the time "from the vernal equinox until the autumnal equinox." His annual return was always something to look forward to.
Already in his mid-twenties, Hannes Alfvén attempted to develop a theory of the origin of cosmic radiation. His paper on this in Nature (1933) and all of his later work is permeated by the principle that theories of cosmical phenomena must agree with known results from laboratory experiments on Earth, because the same laws of nature must apply everywhere.
In considering the cosmic ray problem, he proposed (in 1937) that there exists a galactic magnetic field, but this proposal was generally dismissed. It was later recognized that the galactic magnetic field exists, but apparently without recognition of Hannes Alfvén's original proposal.
His most well-known discovery, of what we now call Alfvén waves, opened a whole new field of research, that of magnetohydrodynamics, which has become an indispensable tool in plasma physics and its applications, not least in astrophysics. It combined electromagnetic theory and fluid dynamics, which until then had been well established but as separate entities. Acceptance of the discovery was slow, and some critics maintained that if the waves described by Alfvén existed, Maxwell would have discovered them. But when, in 1948, Enrico Fermi acknowledged the existence of the new waves, the entire physics community was quick to concur.
Another fundamental contribution by Alfvén is the guiding centre approximation for the motion of charged particles, which has become another invaluable tool throughout the field of plasma physics and much used in cosmical physics
One of his most daring ideas was that of critical velocity in plasma neutral-gas interaction. Introduced as an assumption in a theory of the origin of planets around the sun and satellites around planets, it implies that neutral atoms moving relatively to a collisionless plasma would suddenly become ionized, and their relative motion would brake, at a certain critical velocity. The assumption was in contradiction with contemporary notions in plasma physics, but has later been confirmed experimentally in the laboratory as well as in space.
Some of Hannes Alfvén's ideas are still unaccepted or controversial. Examples are the concept of partial corotation (at a velocity equal to of the Kepler velocity), which he introduced to explain the structure of the Saturnian ring system (and to successfully predict that Uranus would prove to have a ring system). Another example is symmetric cosmology, which implies that the universe as a whole may consist of equal amounts of plasma and antiplasma, separated by thin boundary layers (producing unobservably small annihilation radiation).
Hannes Alfvén and his wife Kerstin took an active interest in global issues such as the environment, population growth, and disarmament. During a period of several years in the 1970s, Hannes Alfvén was President of the Pugwash movement, which, initiated by Albert Einstein and Bertrand Russell, annually gathered eminent scientists from all over the world to discuss such issues. Originally an advocate for the peaceful use of nuclear energy, he became a vigorous opponent when he realized its problems and connections with nuclear arms.
Hannes Alfvén's contribution to the progress of science is not limited to his own work but also includes the extraordinary inspiration that he has given to his many students as well as to colleagues all over the world. I am myself deeply grateful for his immensely valuable inspiration, guidance, and deep personal friendship throughout decades of wonderful collaboration.
Carl-Gunne Fälthammar
Hannes Olof Gösta Alfvén's obituary appeared in Journal of the Royal Astronomical Society 37:2 (1996), 259-260.