Polynomial Reconstruction of the Magnetic Field Observed by Multiple Spacecraft With Integrated Velocity Determination

Abstract

AbstractRecently, a polynomial reconstruction technique has been developed for reconstructing the magnetic field in the vicinity of multiple spacecraft and has been applied to events observed by the Magnetospheric Multiscale (MMS) mission. Whereas previously the magnetic field was reconstructed using spacecraft data from a single time, here we extend the method to allow input over a span of time. This extension increases the amount of input data to the model, improving the reconstruction results and yields an independent estimate of the structure velocity. The effect of this modification, as well as many other options, is explored by comparing reconstructed fields to those of a three‐dimensional particle in cell simulation of magnetic reconnection, using virtual spacecraft data as input. We often find best results using multiple‐time input, a moderate amount of smoothing of the input data, and a model with a reduced set of parameters based on the ordering that the maximum, intermediate, and minimum values of the gradient of the vector magnetic field are well separated. When spacecraft input data are temporally smoothed, reconstructions are representative of spatially smoothed fields. Two MMS events are reconstructed. The first of these was late in the mission when it was not possible to use the current density for MMS4 because of its instrument failure. The second shows a rotational discontinuity without an X or O line. In both cases, the reconstructions yield a visual representation of the magnetic structure that is consistent with earlier studies.