Spectral moments for the analysis of frequency shift, broadening, and wavevector anisotropy in a turbulent flow 3. Space science

Abstract

Turbulence represents essentially random fluctuations that evolve both spatially and temporally, and appear in various geophysical and space science applications. A spectral moment method is proposed to characterize the turbulence energy spectra in the wavevector and frequency domain in the lowest-order sense. The frequency shift velocity and the random sweeping velocity are obtained from the first-order and second-order moments of the wavenumber-frequency spectra. The maximum extension direction and the elliptic spectral shape are obtained from the second-order moments of the wavevector spectra. The algorithm for the spectral moment computation is presented with synthetic energy spectra and solar wind energy spectra.[Figure not available: see fulltext.]