Spectral Properties and Length Scales of Two‐dimensional Magnetic Field Models

Abstract

Two-dimensional (2D) models of magnetic field fluctuations and turbulence are widely used in space, astrophysical, and laboratory contexts. Here we discuss some general properties of such models and their observable power spectra.Whilethefieldlinerandomwalkinaone-dimensional(slab)modelisdeterminedbythecorrelationscale,for 2Dmodels,itischaracterizedbyadifferentlengthscale,theultrascale.Wediscusspropertiesofcorrelationscalesand ultrascales for 2D models and present a technique for determining an ultrascale from observations at a single spacecraft, demonstrating its accuracy for synthetic data. We also categorize how the form of the low-wavenumber spectrum affects the correlation scales and ultrascales, thus controlling the diffusion of magnetic field lines and charged test particle motion. Subject headingg diffusion — magnetic fields — turbulence