A Minimum Energy Fit Method to Reconstruct Photospheric Velocity and Magnetic Diffusivity in Active Regions from Observed Magnetograms and Dopplergrams

摘要: We introduce MEF-R, a generalization of the minimum energy fit (MEF; Longcope, Astrophys. J. 612, 1181, 2004) to non-ideal (resistive) gas. The new technique requires both vector magnetograms and Doppler velocities as input fields. However, in case active regions observed only with Michelson–Doppler Imager (MDI) onboard Solar Heliospheric Observatory (SOHO) such AR 9077, we have access line-of-sight magnetograms. reconstruct two-dimensional maps magnetic diffusivity η(x,y) together velocity components v x (x,y), y z (x,y) under linear force-free field approximation. Computed for very well match r (x,y). find average value 〈η〉≈108 m2 s−1 standard deviation ≈ 1010 s−1. Such high values are be expected at some places since our is actually eddy-diffusivity. Inside do not resemble closely from classical models diffusivity, but they closer η function temperature than electric current density.