Minimum Variance Analysis of Planetary and Interplanetary Plasmas

Abstract:

Characterization of plasma waves typically involves minimum variance analysis (MVA), but without careful consideration MVA-derived results may reflect the choice of analysis parameters rather than the electromagnetic fluctuations. In part one of this presentation, we show Venus Express foreshock wave normal angles calculated using several different ratios of intermediate to minimum variance. The least stringent cases are biased towards higher wave normal angles than the most stringent case. In part two, we hypothesize that this angle bias is inherent to minimum variance analysis and provide a shape-dependent plasma wave uncertainty function. In part three, we test our hypothesis by extending our analysis to magnetometer data from Wind, Parker Solar Probe, and Voyager. Our results will be applicable to missions with high-resolution time series as well as lower frequency wave measurements. By standardizing wave analysis criteria, wave studies will be easier to compare and validate. The wave analysis software we present will be made publicly available in the near future.