THE ZEEMAN EFFECT ON THE SUN
1922; Institute of Physics; Volume: 34; Issue: 197 Linguagem: Inglês
10.1086/123139
ISSN1538-3873
Autores Tópico(s)Solar and Space Plasma Dynamics
ResumoBy Adriaan van Maanen his splendid monograph, Researches in MagnetoOptics/'1 Zeeman begins the eighth chapter with the following words: In discoveries of optics we may always cherish the hope that they will lead ultimately to applications to astronomy. For the Zeeman effect this hope was realized within a dozen years, but its applications up to this time have been confined to only one astronomical body, viz., the Sun. It is true that a few other instances of the doubling of spectral lines have been observed which could possibly be attributed to a magnetic field : Wright2 made an attempt to detect polarization in the multiple bright lines of o Ceti; Adams and Kohlschutter3 did the same in the case of the complex hydrogen bands in Nova Geminorum No. 2 ; and Merrill4 tested the double bright Hs line in y Cassiopeiœ and in b2 Cygni. Definite evidence of a magnetic field was not obtained in any case. Slipher5 announced in 1915 the doubling of Ni, N2, N3, Hs and Hy in the Crab nebula with a maximum distance of the components of 40 A, and in 1918 Campbell and Moore6 published the appearance of double lines in the spectra of ten planetary nebulae; as their experiments made on N. G. C. 7662, in an attempt to detect polarization in the components furnish strong negative evidence, they conclude, however, that the phenomenon is not a simple Zeeman effect. On the other hand, for the Sun the Zeeman effect has now been established with great certainty. Hale's important discovery of magnetic fields in sun-spots was made soon after the introduction of certain improvements in red-sensitive plates by Wallace.7 The spectroheliograph had already made it possible to photograph the Sun's image in the light of a single spectral line, the lines used being ordinarily H and K of calcium and the H8, Hy and H/3 line of hydrogen. 1908 the red-sensitive plates, which enabled Hale and Ellerman to use the high-level Ha line,
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