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Proceedings Paper

Real Time Digital Videomagnetograph At The Aerospace San Fernando Solar Observatory
Author(s): Thomas J. Janssens
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Paper Abstract

Importance of Magnetic Fields In 1908, just 12 years after Zeeman discovered that magnetic fields cause a polarization and shift in certain spectral lines, Hale used this effect to detect the presence of strong magnetic fields in sun-spots. Further studies have shown that magnetic fields exist over the entire surface of the sun in very complicated patterns and determine the structures and motions of the solar plasma such as prominences, spicules, and flares. The very strongest fields of several thousand gauss cause the spectral lines to actually split but for weaker fields the Zeeman shift is only a small fraction of the line width and to measure this shift four steps are required: spectral dispersion or isolation of a magnetically sensitive line, selection of one state of circular polariza-tion, detection of the light intensity, and finally the subtraction of the light in the two opposite states of polarization. Spectral isolation can be achieved by a spectrograph or optical filter; the polarization states can be selected by an electro optic crystal or quarter wave plate with polarizer; the detector can be a phototube, film, or television camera; and the subtraction can be electronic, photographic, or digital. This paper describes a new type of solar magnetograph using digital techniques.

Paper Details

Date Published: 16 April 1973
PDF: 6 pages
Proc. SPIE 0032, Developments in Electronic Imaging Techniques II, (16 April 1973); doi: 10.1117/12.953607
Show Author Affiliations
Thomas J. Janssens, The Aerospace Corporation (United States)

Published in SPIE Proceedings Vol. 0032:
Developments in Electronic Imaging Techniques II
Ralph Zirkind; Sol Nudelman; Alvin Schnitzler, Editor(s)

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