Diagnostics of Small-Scale Magnetic Fields

Abstract

Since Babcock (1953) and Kiepenheuer (1953) invented the photoelectric magnetograph, which maps the distribution of longitudinal magnetic flux across the solar surface by recording the circular polarization in a Zeeman-sensitive spectral line, the spatial resolution of the magnetic-field observations has been gradually increased from about one arcmin to less than one arcsec. Even the seeing limit determined by the earth’s atmosphere can now be overcome by image reconstruction techniques like speckle polarimetry (see next chapter). Each new advance in spatial resolution has revealed new, smaller flux structures not seen before, and we have reasons to believe that this structuring continues well beyond the presently achievable spatial resolution.