Keywords:multi-spacecraft missions, MMS, field analysis, wave vectors, phase shifts
Turner et al. (2017) made use of cross-correlations of SCM quasi monochromatic data between pairs of MMS spacecraft to estimate phase lags and to derive wave vectors of whistler mode chorus elements in the inner magnetosphere. A new approach has been developped to revisite this study. For a cluster of four spacecraft there are six pairs of spacecraft, each one giving raise to a scalar equation relating the vector position R from the first to the second spacecraft, the wave vector K and the phase lag Δφ : R.K=Δφ. A positive weight is attributed to each equation (wj, j=1 to 6). A statistical ensemble of 6-uplets is built and we look for the 6-uplet giving the lowest condition number of matrix M. This procedure warrants the best accuracy of the pseudo-inverse of M and hence the best estimate of the wave vector K. Adding random perturbations to M and Δφ the procedure allows to estimate the uncertainties on K.
Turner, D. L. et al. JGR Space Physics, https://doi.org/10.1002/2017JA024474