Title: Inferring a photospheric velocity field from a sequence of
vector magnetograms: The Minimum Energy Fit

Author_list: Longcope, D. W.

Abstract: We introduce a technique for inferring a photospheric
velocity from a sequence of vector magnetograms.  The technique, called
The Minimum Energy Fit, demands that the photospheric flow agree with
the observed photospheric field evolution according to the magnetic
induction equation.  It selects, from all consistent flows, that with
the smallest overall flow speed by demanding that it minimize an energy
functional.  Partial or imperfect velocity information, obtained
independently, may be incorporated by demanding a velocity consistent
with the induction equation which minimizes the squared difference with
flow components otherwise known. The combination of low velocity and
consistency with the induction equation are desirable when using the
magnetogram data and associated flow as boundary conditions of a
numerical simulation.  The technique is tested on synthetic
magnetograms generated by specified flow fields and shown to yield
reasonable agreement.  It also yields believable flows from
magnetograms of NOAA AR8210 made with the Imaging Vector Magnetogram at
the Mees Solar Observatory.