by C.-G. Fälthammar, Royal Institute of Technology, Stockholm; and A. J. Dessler, University of Arizona, Tucson
Nobel Prize recipient Hannes Alfvén first discovered his passion for science as a high school student in Sweden. Throughout his career he made a number of theoretical findings that established magnetohydrodynamics—the study of the behavior of space plasma—as a field of research.
Hannes Alfvén was born on May 30, 1908, in Norrköping, Sweden. The son of Johannes Alfvén and his wife, Anna-Clara Romanus, Hannes had an exceptional family background. His mother was one of the first female physicians in Sweden, a remarkable achievement at that time. His father, also a practicing physician, had a strong interest in science. One of Alfvén's uncles, Hugo Alfvén, was a famous composer. Another was an inventor, and a third, an agronomist by profession, was very interested in astronomy and was far ahead of his contemporaries in formulating ideas about the environment and its problems.
According to Alfvén's own account, two experiences in his youth, one at home and one in school, influenced his intellectual development and his professional career. One was the gift at an early age of a popular book on astronomy, written by the French astronomer Camille Flammarion. This he read passionately, and it kindled a lifelong interest in astronomy and astrophysics. The other was his membership in his school's radio club, where he built radio receivers. There was no nearby radio station, and the one station in Stockholm was too weak to be received with primitive equipment in Norrköping, Sweden. The most promising was the strong station in Aberdeen, Scotland. Alfvén has described, with some passion, the thrill he felt when a few faint notes of music emerged out of the atmospheric noise and could be identified as coming from Aberdeen.
After high school, Alfvén entered the University of Uppsala in Sweden, where he studied mathematics and experimental and theoretical physics. While working in a physics department that was focused on spectroscopy, he demonstrated his characteristic intellectual independence by choosing research topics that we would now classify as nuclear physics and electronics. The title of his doctoral thesis (1932), which he said was a direct continuation of his radio club activities, was "Ultra-Short Electromagnetic Waves." Alfvén, again following his own visions, moved into electronics and astronomy just when everyone else was moving into nuclear physics. For the next eight years, he worked first at the University of Uppsala and then at the Nobel Institute in Stockholm. During this period, he spent two brief periods abroad: a few months in Berlin and a half-year or so in Cambridge.
While at the Nobel Institute, Alfvén became increasingly interested in the acceleration of
charged particles to high energies, and especially to the extreme energies of cosmic
rays. His early attempt to develop a theory on the origin of cosmic radiation was published in
Nature in 1933. The paper reflects an important aspect of Hannes Alfvén's approach to
science that he maintained throughout his career. It criticized earlier speculations concerning cosmic
radiation because they did not "seem to be in accordance with the latest experimental results." In the
paper Alfvén also stated that it should be possible to "explain the origin of the cosmic rays,
introducing no new hypotheses, and only applying the kinetic gas theory to the conditions of world space."
Fig. 1. A thoughtful, self-confident Hannes Alfvén in 1942. Around this time he was doing the work that would be published in his landmark book, Cosmical Electrodynamics.
In 1940, at only 32 years of age, Hannes Alfvén was appointed Professor of Electromagnetic Theory and Electric Measurements at the Royal Institute of Technology, Stockholm. He once said that, at the time, he attached more significance to joining the Faculty of the Royal Institute than to the award of the Nobel Prize some 30 years later. In 1942 he developed what later became known as the Alfvén theory. As a result of the rapid evolution of his interests, his own professorship changed, first to Electronics in 1946, and then to Plasma Physics in 1963. His vigorous leadership led to the creation of a number of new professorships and departments. The three departments that directly trace their origin to his work now form a separate entity within the Royal Institute of Technology: the Alfvén Laboratory, which was founded in 1990.
Alfvén accepted a professorship at the University of California, San Diego, in 1967 and he divided his time so that he was at the Royal Institute "from the Vernal Equinox until the Autumnal Equinox" and at the University of California from fall until spring. He wanted to avoid crossing the Atlantic at other times, and he yielded only twice: once for the birth of a grandchild and once to receive his Nobel Prize. His involvement in science continued well beyond his formal retirement in 1973. He ended his seasonal shifts and settled in Sweden in 1988.
Alfvén usually worked one step ahead of the forefront of science. For example, quite ahead of his time, Alfvén gave a simple, intuitive demonstration of how a belt of energetic charged particles can maintain stable circulation around a magnetized planet such as the Earth. Before Alfvén's discoveries, particle trajectories had to be calculated by numerical integration, and without the benefit of digital computers! The tools Alfvén introduced brought physical imagery and simplified mathematical effort into what had been a specialized field of mathematical drudgery. Thus he developed the basic tools we use today to describe the Van Allen radiation belt two decades before the belt was discovered. He proposed a cosmic ray acceleration mechanism that is now known as the Fermi Mechanism—although Alfvén did it before Fermi. And he fought for years to make scientists aware of the importance of electric fields and currents in space.
Alfvén was always in the lead. His impact was such that anyone who attends a meeting on magnetospheric physics, solar physics, or space plasma physics invariably hears his name mentioned. When his ideas on the existence of electric fields that were perpendicular to magnetic fields were being questioned, if not attacked, he added "double layers," which are regions of strong electric fields parallel to the magnetic field in the plasma of space. His magnetic-field-aligned electric field, in combination with field-aligned currents originating in what is now called the Alfvén layer, is now accepted as crucially important for the acceleration of the charged particles that cause the polar aurora. He also proposed astrophysical applications for his double layers, and a new mechanism for the interaction of plasma and un-ionized gas in relative motion. In an entirely different arena, he was first to offer a plasma-physics theory for the formation of comet tails in the expanding solar plasma known as the solar wind.
Hannes Alfvén possessed a gift that allowed him to extract important results from specific problems. It is a mark of his genius that his initial understanding came primarily from physical reasoning; the mathematical demonstrations came only after he had, in his mind's eye, determined the physical process. His discovery of Alfvén waves is, in many ways, representative of his approach. It grew out of a specific problem, namely that of sunspots. Alfvén first determined that it was possible to propagate electromagnetic waves in a highly conducting plasma. (This, he claimed, was the easy part.) Only then did he develop the mathematical demonstrations. The idea that such waves were possible ran contrary to the conventional thought of the time because it was taught that electromagnetic waves could propagate no more than a skin-depth, about a wavelength, into a good conductor. But Alfvén had found, by pure power of intellect, an entirely new propagation mode. He discovered how electromagnetic waves can propagate without damping in a plasma of arbitrarily high conductivity.
His work on the cosmic-ray problem led him to propose in 1937 the existence of a galactic magnetic field. Because interstellar space was then believed to be a vacuum, it was widely thought that there could be no interstellar magnetic field because the magnetic field of individual stars would be too weak to fill interstellar space. Alfvén proposed that interstellar space could contain enough plasma to carry electric currents that would produce the magnetic field. Only much later was the existence of the galactic magnetic field confirmed, and, as is typical of many of Alfvén's contributions, without formal recognition that the idea has been his.
Alfvén thought that theories of cosmical phenomena must agree with laboratory experiments. He later broadened his definition of "laboratory" to include space itself. He believed that the laws of nature apply everywhere, and a key to his success seems to be the fresh perspective that came from applying laboratory results to problems in space physics and astrophysics.
Considering Alfvén's many fundamental accomplishments, it now seems bizarre that, until he was awarded the Nobel Prize, he was not well regarded by other leading scientists. For example, in 1939 he wrote a remarkable paper in which he proposed a theory for magnetic storms and auroras. This paper, which lays out now accepted basic ideas on how plasma flows around a dipole magnetic field to create Birkeland currents that flow in and out of the auroral zone, was denied publication in a premier journal of the day because it disagreed with the theories of space physics pioneer Sydney Chapman and his colleagues. To get this and other important early papers published, he eventually turned to journals that did not enjoy international readership. Most of Alfvén's ideas were finally made known to the scientific community through his marvelous book, Cosmical Electrodynamics, which was published in 1950. This book has inspired a number of books by others that incorporate similar approaches and content.
It usually took years for Alfvén's ideas to be accepted. For example, his discovery of
hydromagnetic waves was presented in an admirably simple and clear mathematical form in a letter to
Nature published in 1942. Acceptance came suddenly some six years later when, as Alfvén
recounted, at the end of a seminar he gave at the University of Chicago in 1948, the famous physicist
Enrico Fermi nodded his head and said "of course" and, according to Alfvén's account, the prestige
of Fermi was such that "the next day, everyone nodded and said, 'of course'." Some of Hannes
Alfvén's ideas are still controversial. One example is his idea that the universe consists of equal
amounts of matter and antimatter separated by thin boundary layers.
Fig. 2. Hannes Alfvén is being handed the Nobel Prize by the King of Sweden. The lady wearing the tiara is the Queen.
Besides the Nobel Prize and AGU's highest honor, the Bowie Medal, Alfvén received other honors. He was one of a select few who were members of both the American and the Soviet Academies of Sciences. With his wife Kerstin, he also took an active interest in important matters outside science, especially those related to environment, population growth, and disarmament. One result of these interests was a series of books that Hannes wrote, some together with Kerstin. When nuclear power first became a possibility, Alfvén supported its development for commercial use. However, within a few years, when disadvantages came to light, Alfvén became a vigorous opponent. In Sweden, his persuasive support of the antinuclear position is acknowledged as an important element in Sweden's eventual decision to abandon its nuclear power program.
Alfvén contributed to the progress of science not only through his own work but also through the inspiration he gave to his many students as well as to colleagues all over the world. After a fulfilling life and career replete with remarkable achievements, he died in his home in Djursholm, Sweden, on April 2, 1995, shortly before his 87th birthday. His death has left many of us with a feeling of great loss but also of deep gratitude for all that he has meant as a scientist and as a friend.
Source: Eos, Vol. 76, Sept. 26, 1995, p. 385.
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