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Vegard, Lars

VEGARD, LARS

(b. Vegorshei, Norway, 3 February 1880; d. Oslo, Norway, 21 December 1963)

physics, cosmic geophysics.

Lars Vegard, who introduced modern experimental physics into Norway, grew up in southern Norway on the farm of his parents, Nils Gundersen Grasaasen and Anne Grundesdatter Espeland. Although his father was a farmer and his own early schooling was irregular, Vegard moved to Christiania (now Oslo) to attend the gymnasium. In 1899 he enrolled at Royal Frederik University (now University of Oslo), where he majored in physics. Upon receiving his bachelor’s degree in 1905, he was asked to become an assistant to Kristian Birkeland, whose re search on northern lights was to influence Vegard’s career.

Upon receiving a university fellowship in 1908, Vegard left for Cambridge, where he learned experimental techniques from J.J. Thomson and worked on problems involving cathode rays. In 1910 he became instructor in physics at Royal Frederik University, but he soon received a fellowship that allowed him to spend the academic year 1911–1912 in Wilhelm Wien’s laboratory at Würzburg. Here Vegard worked with canal (positive) rays, beginning an experimental study of their light emission that became the basis for his doctoral dissertation at Royal Frederik University, “Über die Lichterzeugung in Glimmlicht und Kanalstrahlen.” After receiving his doctorate in 1913 he was named docent, and in 1918, after Birkeland’s death, professor of physics. In addition to his pioneering work on the spectral analysis of northern lights, Verergard introduced the ideas and organizational forms of modern physics into Norway.

In 1915 he married Inger Hervora Petersen; they had a daughter, Anne Lise. Although he spent his adult life in Oslo, Vegard never lost the strong attachment to nature developed during his childhood. He went moose hunting every autumn until he was seventy years old, he skied until the end of his life, and among German physicists he acquired a reputation as an extraordinary sportsman.

Vegard’s research career owed much to his first experiences in science. Birkeland had proposed in 1896 that northern lights arose from the effects of cathode rays emitted by the sun that are caught in the earth’s magnetic field. In the university’s cellar he built a model to produce analogies to northern to lights and related cosmic-geophysical phenomena. Birkeland used private funds to hire assistants, which allowed him to recruit some of the brightest young natural science students for his projects; Vegard was one of them.

Vegard first analyzed data that Birkeland had obtained on expeditions to northern Norway in an effort to find relations between magnetic storms and northern lights. Subsequently his doctoral research on canal rays enabled him to open new avenues of inquiry for understanding northern lights. Vegard reasoned that the solar emissions must be electrically neutral, and therefore must consist of both negative and positive particles. Moreover, he associated the fact that northern lights often display a sharp lower boundary with similar experimental results exhibited by α-particles passing through air. If positively charged particles were indeed responsible for northern lights, then the frequencies of their spectral lines should shift with their speed.

Vegard decided to make spectral photographs of northern lights, a task that required considerable experimental skill, great patience, and physical endurance. Hour after hour, night after night, he had to stand in intense cold, holding specially constructed spectrographs toward the ever-moving northern lights. In 1939 he finally identified hydrogen lines in the lights’ spectrum, and in 1948 he could show the Doppler effect in the “proton” northern lights.

While constantly improving the spectral techniques, Vegard was able to provide the first realistic models of the atmosphere’s composition and structure between 80 and 1,000 kilometers. One feature, however, seemed to defy explanation: the bright “green northern light line.” No known atmospheric gas could account for its appearance. In the early 1920’s Vegard published a theory of the physical conditions in the upper atmosphere in which he assumed that in the extreme cold, oxygen and nitrogen occurred in frozen crystalline forms. The bright green spectral line, he thought, might well be the result of frozen nitrogen.

Vegard visited Heike Kamerlingh-Onnes’s cryogenics laboratory in Leiden, where he made spectral analyses of the light emitted by frozen nitrogen stimulated by elctrons. In these experiments he discovered phosphorescence of solid nitrogen and the spectral band that now is called the Vegard-Kaplan band. This discovery paved the way to studies of “trapped radicals.” Vegard’s conclusion on the origin of the green line, however, was mistaken. It arises from a from of oxygen occurring only in the special conditions of the upper atmosphere.

Although most of his research was circumscribed by his interest in northern lights, Vegard’s interest in modern physics brought him into contact with other areas to which he made contributions. Upon learning of X-ray diffraction, he traveled to Cambridge and to Leeds, where W.H. Bragg was professor, to learn the new technique. In 1916 he and a number of assistants began a series of studies on crystal structure using X-ray diffraction. This work also brought him into contact with the Bohr-Sommerfeld atomic model; he published several articles on the relation between X-ray spectra and the periodic system.

Throughout his career Vegard endeavored to obtain better facilities and opportunities for physics research and education in Norway. He initiated plans and obtained funding from the Rockfeller Foundation for a northern lights observatory at Tromsø, northern Norway’s major city. This facility, opened in 1930, paved the way for the founding of the Norwegian Institute for Cosmic Physics, of which Vegard served as chairman and major inspirational force until he retired in 1955. Vegard also played a role in selecting Blindern as the site for the new university campus in Oslo and helped plan the new physics and chemistry building, which opened in 1935. He was a major figure in obtaining a nuclear physics laboratory for the physics institute; he also was twice rector of the Faculty of Mathematics and Natural Sciences in the 1930’s.

BIBLIOGRAPHY

I. Original Works. Vegard’s writings are listed in BoggendotfT, V, 1303; VI, 2740–2741. Vegard’s autobiographic essays are in Studentenc fra 1899 (1924), 333–335, 1949), 210–212.

II. Secondary Literature. J. Holtsmark, “Minnetale over professor dr. Lars Vegard,” in Det Norske viden-skaps-akademi i Oslo, Arsbok 1966, 53–58; Gotfred Kvifte, “Lars Vegard,” in Fra fysikens verden, 26 (1964), 1–4; and J. Holtsmark, “Lars Vegard,” in Norsk biografisk leksikon, XVII (Oslo, 1975), 524–529.

Robert Marc Friedman

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