Systematic Uncertainties in Plasma Parameters Reported by the Fast Plasma Investigation on NASA's Magnetospheric Multiscale Mission

Abstract

Systematic uncertainties in the conversion of measured counts to phase space density by charged particle instrumentation result in errors in reported plasma moments (e.g., density, velocity, and temperature). Unlike previous particle instrumentation that relied on a spacecraft spin to sample all look-directions, the Fast Plasma Investigation (FPI) suite on NASA's Magnetospheric Multiscale mission nearly simultaneously images the full sky. This configuration results in unprecedented time resolution but also introduces the possibility of spin tones in plasma moments, in particular electron bulk velocity. Here we characterize the effect of systematic linear errors of corrected FPI phase space densities on its reported plasma moments. We find that the flat-fielding correction factors (i.e., scale factor errors) of FPI are typically accurate to within a few percent but can nonetheless result in significant spin tones in magnetospheric plasmas.