Wave field analysis by magnetic measurements at satellite arrays: generalized minimum variance analysis

Abstract

The main goal of the CLUSTER mission with four identical spacecraft is the spatial resolution of plasma structures. For the determination of the wave vectors of a wave field from four positions classical Fourier analysis is inappropriate. We develop a generalized minimum variance technique which gives a high wave vector resolution though the spatial grid is restricted to only a few sampling positions. This technique uses the amplitude and phase information of the magnetic field from the four satellite positions and determines the optimum wave field corresponding to the measured data. The divergence-free nature of the magnetic field is used as a constraint. Using the magnetic data measured at four positions up to four different wave vectors at one frequency can be uniquely resolved.