The figure below was obtained by scanning across the sunspot, on the right half of the image, with a spectroscope. The left half of the image shows that the absorption line splitting is largest in the center of the sunspot, where the magnetic field is strongest. To determine the strength of the magnetic field at that point, we need only measure the distance between the split absorption line. We can then map the magnetic field of the sunspot by measuring the distance between the splitting of the absorption line at each point on the spectral image and matching that point with the white light image. Measuring the direction of the magnetic field, to get the full vector, is a bit more difficult than just finding the magnitude.
Waves have a preferred direction of travel and a particular vibration.
Vector magnetographs analyze the directions of vibration of the light coming from sunspots and infer from that the direction of the magnetic field. Pictured here, is the Marshall Space Flight Center's vector magnetograph. H-alpha light has a wavelength of 656 nm and is created within the chromospheric layer of the solar atmosphere. Here for the Previous Page To return to Slide Show Page 1, click here . To return to the Sun in Time home page, click here .