Energy spectrum of small-scale solar magnetic fields

On the basis of observations that magnetic flux is transported by fluid motions at the photospheric level of the Sun, the possible interpretation of the energy spectra of small-scale solar magnetic fields in terms of a passive response of the (longitudinal) magnetic field to turbulent fluid motions is examined. In consideration of the prevailing physical conditions, a theory is developed which accounts for the two-dimensional passive response of longitudinal magnetic fields to a three- dimensionally isotropic turbulent convection at the level of vanishing vertical velocity. The theoretical results are compared with the energy spectra of small-scale magnetic fields obtained from longitudinal magnetograms for typical active, quiet, and mixed regions of the Sun. It is shown that the observed spectra can be interpreted in terms of the theory developed with the choice of eddy kinematic viscosity 1014 cm2 5 -` and eddy magnetic diffusivity 1012 cm2 -1, including differences in the spectral shape for different regions of solar activity. The details of the theory are described together with discussions on the limitations and other implications of the results. Subject headings: hydromagnetics - magnetic fields, solar - turbulence