Spiky electric and magnetic field structures in flux rope experiments

Abstract

Magnetic flux ropes are structures that are common in the corona of the sun and presumably all stars. They can be thought of as the building blocks of solar structures. They have been observed in Earth's magnetotail and near Mars and Venus. When multiple flux ropes are present magnetic field line reconnection, which converts magnetic energy to other forms, can occur when they collide. The structure of multiple magnetic ropes, the interactions between multiple ropes, and their topological properties such as helicity and writhing have been studied theoretically and in laboratory experiments. Here, we report on spiky potential and magnetic fields associated with the ropes. We show that the potential structures are chaotic for a range of their temporal half-widths and the probability density function (PDF) of their widths resembles the statistical distribution of crumpled paper. The spatial structure of the magnetic spikes is revealed using a correlation counting method. Computer simulation suggests that the potential structures are the nonlinear end result of an instability involving relative drift between ions and electrons.

Interfaces and mixing: Nonequilibrium transport across the scales

“…This issue reports significant successes that have been achieved recently in understanding interfaces, mixing, and nonequilibrium dynamics based on theoretical analysis, large-scale numerical simulations, laboratory experiments, and technology development (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34). These include theoretical approaches for handling complex multiscale, nonlocal, and statistically unsteady dynamics and boundary value problems; developments of efficient Eulerian and Lagrangian methods of large-scale numerical modeling; advancements in laboratory experiments in low-and high-energy density regimes; and possibilities for dramatic improvements in precision, accuracy, dynamic range, reproducibility, and data acquisition rate with the use of modern technologies (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34).…”

“…These works represent frontier research in interaction of molecules and chemical reactions, interfacial dynamics and nonequilibrium processes, fluid turbulence and turbulent mixing, supernovas and nuclear synthesis, formation of fluid phases at molecular scales, first-principlesbased reaction kinetics, ion transport of nanoscales, electric and magnetic fields structures, dynamics of high-energy density plasmas, subdiffusive and superdiffusive transport, formation of vortices in geophysical flows, diffusiophoresis of charged particles, and electron transport in macromolecules. They motivate the discussions of rigorous mathematical problems, theoretical approaches, and state-of-the-art numerical simulations along with advanced experimental methods and technological applications (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32).…”

“…The contributions in this issue include 6 perspective papers and 7 research papers (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32). They are ordered from perspective to research papers, from macroscopic to microscopic scales, and from fundamentals to applications.…”

“…The research paper by Gekelman et al (28) analyzes magnetic flux ropes in plasma experiments. Such structures are commonly observed in the corona of the Sun, the Earth's magneto-tails, and near Mars and Venus.…”

Magnetic reconnection in the era of exascale computing and multiscale experiments

“…Magnetic reconnection in high-temperature, toroidal fusion experiments occurs usually in the multiple X-line collisionless regimes 5,255 at relatively large Lundquist number S and plasma size λ , but with limited diagnostics accesses. In contrast, specially implemented diagnostics of many ongoing reconnection experiments in low-temperature linear devices enable detailed studies of 3D electromagnetic fields 272,273 , quasi-separatrix layers 274 , electron and ion kinetics 275 , or noninvasive magnetic field measurements 276 at relatively modest S and λ values. S or λ can be large for the reconnection experiments in high-energy-density (HED) plasmas based on Z pinches 86,277 or lasers 271,278 , but they are driven by converging flows at high β , in contrast to the typical impulsive reconnection which is driven magnetically at low β .…”