The most common way is through the Zeeman splitting of certain spectral lines in the presence of a magnetic field. The amount of splitting is a measure of the field strength. And the state of polarization of the light in the spectral line correlates with the polarity of the field. At the Kitt Peak Solar Observatory, daily magnetograms are obtained of the Sun which show the polarity and strength of the magnetic fields over the solar disk. One of these instruments is the Marshall Space Flight Center Vector Magnetograph. For a daily magnetogram of the full Sun, visit the Mt. Wilson Observatory 150-foot solar telescope which publishes daily images, weather permitting. The above image was obtained from their archive. Red colors indicate strengths of -20 gauss. Blue indicates +20 gauss field strengths.
Copyright 1997 Dr. Sten Odenwald
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