The comparison between Advanced Composition Explorer (ACE) solar wind data and simulations of magnetohydrodynamic (MHD) turbulence shows a good agreement in the waiting-time analysis of magnetic field increments. Similarity between classical discontinuity identification and intermittency analysis suggests a dynamical connection between solar wind discontinuities and intermittent MHD turbulence. Probability distribution functions of increments in ACE data and in simulations reveal a robust structure consisting of small random currents, current cores, and intermittent current sheets. This adds to evidence that solar wind magnetic structures may emerge fast and locally from MHD turbulence.
[1] We examine statistics of rapid spatial variations of the magnetic field in simulations of magnetohydrodynamic (MHD) turbulence, by analyzing intermittency properties, and by using classical methods for identifying discontinuities. The methods identify similar structures, and give very similar event distribution functions. When the results are scaled to the correlation length, the average waiting times agree with typically reported waiting times between solar wind discontinuities. Thus discontinuities may be related to flux tube boundaries and intermittent structures that appear spontaneously in MHD turbulence.
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. While the field line random walk in a one-dimensional (slab) model is determined by the correlation scale, for 2D models, it is characterized by a different length scale, the ultrascale. We discuss properties of correlation scales and 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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.