Determination of Magnetic Diffusivity from High‐Resolution Solar Magnetograms

The magnetic diffusivity in the solar photosphere is determined by applying a new method to the magnetic induction equation. The magnetic field evolution is specified by a time sequence of high-resolution magnetograms of plage regions, taken by Hinode/SOT and SOHO/MDI. The mean value of magnetic diffusivity determined from SOT magnetograms with the smallest pixel size of 116 km is about -->0.87 ? 0.08 km2 s?1. This is the smallest value that has been empirically determined so far. High-resolution and full-disk MDI magnetograms with the pixel sizes of 440 and 1400 km yielded larger values of -->4.4 ? 0.4 and -->18 ? 7.4 km2 s?1, respectively. The measured diffusivity values at different length scales are consistent with a turbulent cascade that ends at a resistive dissipation scale of about 30 km. The results suggest that turbulent magnetic diffusivity should be taken into account in the analysis of the observed rate of magnetic flux cancellation in the photosphere.