High-Latitude Plasma Convection Based on SuperDARN Observations and the Locally Divergence Free Criterion

A new technique for estimating the global-scale pattern of magnetospheric convection in the ionosphere is presented. The technique uses the Super Dual Auroral Radar Network line-of-sight velocity observations combined with an empirical convection model and the assumption that the resulting velocity field is divergence free. In contrast to other techniques for convection estimation, it does not express the velocity field in terms of known basis vectors and it does not assume that the velocity can be determined from a static potential. The velocity is estimated by applying Bayesian inverse theory to the input data, model, and constraints. Linear equations for the plasma velocity at every point in the domain are solved simultaneously in a least squares sense. Application of the technique results in convection patterns with spatial resolution equal to the calculation grid spacing. The resulting patterns conform with expectations based on the observed interplanetary magnetic field conditions and display features that show close correspondence to simultaneously observed features in the auroral luminosity.