A5049403147- Solar and Space Plasma Dynamics
- Ionosphere and magnetosphere dynamics
- Magnetic confinement fusion research
- Geomagnetism and Paleomagnetism Studies
- Astro and Planetary Science
- Plasma Diagnostics and Applications
- Earthquake Detection and Analysis
- Magnetic Field Sensors Techniques
- Fluid Dynamics and Turbulent Flows
- Laser-induced spectroscopy and plasma
- Magnetic Properties and Applications
- Geophysics and Gravity Measurements
- Gas Dynamics and Kinetic Theory
- Magnetic properties of thin films
- Magnetic Properties of Alloys
- Characterization and Applications of Magnetic Nanoparticles
- Particle Dynamics in Fluid Flows
- Particle accelerators and beam dynamics
- Atomic and Subatomic Physics Research
- Atomic and Molecular Physics
- Electron and X-Ray Spectroscopy Techniques
- Atmospheric Ozone and Climate
- Dust and Plasma Wave Phenomena
- Particle Accelerators and Free-Electron Lasers
- Geophysics and Sensor Technology
University of Delaware
2016-2025
Delaware State University
2022
University of California, Berkeley
2022
University of Southampton
2022
Imperial College London
2022
Planetary Science Institute
2022
University of California, Los Angeles
2022
John Wiley & Sons (United States)
2016
Charles River Laboratories (Netherlands)
2016
Space Science Institute
2013
The Geospace Environmental Modeling (GEM) Reconnection Challenge project is presented and the important results, which are in a series of companion papers, summarized. Magnetic reconnection studied simple Harris sheet configuration with specified set initial conditions, including finite amplitude, magnetic island perturbation to trigger dynamics. evolution system explored broad variety codes, ranging from fully electromagnetic particle cell (PIC) codes conventional resistive...
Magnetic reconnection is a fundamental physical process in plasmas whereby stored magnetic energy converted into heat and kinetic of charged particles. Reconnection occurs many astrophysical plasma environments laboratory plasmas. Using measurements with very high time resolution, NASA's Magnetospheric Multiscale (MMS) mission has found direct evidence for electron demagnetization acceleration at sites along the sunward boundary Earth's magnetosphere where interplanetary field reconnects...
A Sweet-Parker-type scaling analysis for asymmetric antiparallel reconnection (in which the reconnecting magnetic field strengths and plasma densities are different on opposite sides of dissipation region) is performed. Scaling laws rate, outflow speed, density outflow, structure region derived from first principles. These results independent mechanism. It shown that a generic feature X-line stagnation point not colocated, leading to bulk flow across X-line. The verified using...
The Geospace Environment Modeling (GEM) Challenge Harris current sheet problem is simulated in 2 1/2 dimensions using full particle, hybrid, and Hall MHD simulations. same gross reconnection rate found all of the simulations independent type code used, as long term included. In addition, mechanism which breaks frozen‐in flux condition, whether it electron inertia or grid scale diffusion. insensitivity to condition a consequence whistler waves, control plasma dynamics at small scales where...
Three-dimensional particle simulations of magnetic reconnection reveal the development turbulence driven by intense electron beams that form near x-line and separatrices. The collapses into localized three-dimensional nonlinear structures in which density is depleted. predicted structure these holes compares favorably with satellite observations at Earth's magnetopause. birth death their associated electric fields lead to strong scattering energization, whose understanding critical...
An unsolved problem in plasma turbulence is how energy dissipated at small scales. Particle collisions are too infrequent hot plasmas to provide the necessary dissipation. Simulations either treat fluid scales and impose an ad hoc form of dissipation (e.g., resistivity) or consider arising from resonant damping amplitude disturbances where rates found be comparable that predicted linear theory. Here, we report kinetic simulations span macroscopic down motion electrons. We find turbulent...
Particle-in-cell simulations of collisionless magnetic reconnection are presented that demonstrate remains fast in very large systems. The electron dissipation region develops a distinct two-scale structure along the outflow direction. Consistent with reconnection, length current layer stabilizes and decreases decreasing mass, approaching ion inertial for proton-electron plasma. Surprisingly, electrons form super-Alfvénic jet decoupled from field extends distances downstream x line.
Collisionless magnetic reconnection is studied using a 2 1/2‐dimensional hybrid code including Hall dynamics and electron inertia. The simulations reveal that the dissipation region develops two‐scale structure: an inner outer ion region. Close to X line with scale of c /ω pe , collisionless skin depth, where flows completely dominate those ions frozen‐in flux constraint broken. Outside this encompassing rest region, which scales like pi inertial length, electrons are field but not, allowing...
The present study examines the temporal structure of fast flow in plasma sheet using both observations and simulations. data analysis part adopts strictest criterion ever for satellite location so that selected flows are mostly convective. From Geotail measurements at X > −31 R E , 818 earthward‐flow 290 tailward‐flow events selected. Superposed epoch analyses conducted with two different reference times: start time a sharp change B z component. results summarized as follows: (1) magnetic...
Hybrid simulations with electron inertia, along analytic scaling arguments, are presented which demonstrate that magnetic reconnection remains Alfvénic in a collisionless system even as the macroscopic scale length of becomes very large. This fast is facilitated by whistler physics present near x‐line. The rate found to be universal constant corresponding an inflow velocity towards x‐line around 0.1 c A .
Simulations of collisionless magnetic reconnection show a dramatic enhancement the nonlinear rate due to formation an open outflow region. We link this configuration dispersive whistler and kinetic Alfvén wave dynamics at small scales. The roles these two waves are controlled by dimensionless parameters, which allow us identify regions fast slow reconnection.
We present particle‐in‐cell simulations of collisionless magnetic reconnection in a system (like the magnetopause) with large density asymmetry across current layer. In presence an ambient component field perpendicular to plane gradient creates diamagnetic drift that advects X‐line electron velocity. When relative between ions and electrons is order Alfvén speed scale outflows from necessary for fast cannot develop suppressed. discuss how these effects vary both plasma β shear angle...
Three‐dimensional (3‐D) particle simulations are performed in a double current layer configuration to investigate the stability of sheets and boundary layers which develop during magnetic reconnection antiparallel fields collisionless plasma. The strong that near x line remain surprisingly laminar, with no evidence turbulence associated anomalous resistivity or viscosity. Neither electron shear flow instabilities nor kink‐like instabilities, have been observed these earlier simulations,...
Systematic analysis of numerical simulations two-dimensional magnetohydrodynamic turbulence reveals the presence a large number $X$-type neutral points where magnetic reconnection occurs. We examine statistical properties this ensemble events that are spontaneously generated by turbulence. The associated rates distributed over wide range values and scales with geometry diffusion region. Locally, these can be described through variant Sweet-Parker model, in which parameters externally...
The production of energetic electrons during magnetic reconnection is explored with full particle simulations and analytic analysis. Density cavities generated along separatrices bounding growing islands support parallel electric fields that act as plasma accelerators. Electrons because their low mass are fast enough to make multiple passes through these acceleration therefore capable reaching relativistic energies.
Particle simulations and analytic arguments are presented to demonstrate that the electron dissipation region, including physics which breaks frozen‐in condition, does not affect rate of reconnection in collisionless plasma. The result is a general consequence quadratic nature dispersion character whistler waves, control plasma dynamics at small scales. instead controlled by length scales much greater than region.
Magnetic reconnection plays a key role in the circulation of plasma through Earth's magnetosphere. As such, magnetotail is an excellent natural laboratory for study and particular diffusion region. To address important questions concerning observational occurrence rates average properties, Cluster data set from 2001–2005 has been systematically examined encounters with X lines ion regions magnetotail. This survey 175 passes resulted sample 33 correlated field flow reversals. Eighteen events...
High resolution kinetic simulations of collisionless plasma driven by shear show the development turbulence characterized dynamic coherent sheetlike current density structures spanning a range scales down to electron scales. We present evidence that these are sites for heating and dissipation, stronger signify higher dissipation rates. Evidently, scale plasma, like magnetohydrodynamics, becomes intermittent due sheet formation, leading expectation in astrophysical space plasmas may be highly...
The results of large-scale, particle-in-cell simulations are presented on the role Hall electric and magnetic fields structure electron dissipation region outflow exhaust during collisionless reconnection antiparallel fields. reveal that whistler wave plays key in driving electrons away from x-line. Further downstream consists a narrow super-Alfvénic jet, which remains collimated far x-line, flanked by pedestal whose width increases monotonically with increasing distance downstream. open...
The heating of ions downstream the x‐line during magnetic reconnection is explored using full‐particle simulations, test particle and analytic analysis. Large‐scale simulations reveal that ion temperature increases sharply across boundary layer separates upstream plasma from Alfvénic outflow. This layer, however, does not take form a classical switch‐off shock as discussed in Petschek model, so cannot be calculated magnetohydrodynamic, slow‐shock prediction. Test trajectories fields crossing...