Tangential field changes in the great flare of 1990 May 24

We examine the great (solar) flare of 1990 May 24 that occurred in active r egion NOAA 6063. The Big Bear Solar Observatory videomagnetograph Stokes V and I images show a change in the longitudinal field before and after the f lare. Since the flare occurred near the limb, the change reflects a rearran gement of the tangential components of the magnetic field. These observatio ns lack the 180 degrees ambiguity that characterizes vector magnetograms.