We study properties of magnetohydrodynamic (MHD) eigenmodes by decomposing the data MHD simulations into linear modes - namely Alfven, slow magnetosonic, and fast magnetosonic modes. drive turbulence with a mixture solenoidal compressive driving, while varying Alfven Mach number (MA), plasma beta, sonic from sub-sonic to trans-sonic. find that proportion in mode increases increasing forcing. This can also become dominant fraction mixture. The anisotropy is analyzed means their structure...

Simulations of decaying magnetohydrodynamic (MHD) turbulence are performed with a fluid and kinetic code. The initial condition is an ensemble long-wavelength, counter-propagating, shear-Alfv\'{e}n waves, which interact rapidly generate strong MHD turbulence. total energy conserved the rate turbulent decay very similar in both codes, although code has numerical dissipation whereas dissipation. inertial range power spectrum index codes. shows perpendicular wavenumber spectral slope...

From numerical solutions of a gyrokinetic model for ion temperature gradient turbulence it is shown that nonlinear coupling dominated by three-wave interactions include spectral components the zonal flow and damped subdominant modes. Zonal flows dissipate very little energy injected instability, but facilitate its transfer from unstable mode to dissipative modes, in part due small frequency sum such triplets. Although transferred higher wave numbers, consistent with shearing, large fraction...

Abstract This paper studies cosmic-ray (CR) transport in magnetohydrodynamic (MHD) turbulence. CR is strongly dependent on the properties of magnetic We perform test particle simulations to study interactions with both total MHD turbulence and decomposed modes. The spatial diffusion coefficients pitch angle scattering are calculated from trajectories Our results confirm that fast modes dominate propagation, whereas Alfvén slow much less efficient have shown similar pitch-angle rates....

A broad sample of fluid models for instability-driven plasma turbulence is surveyed to determine whether saturation involving damped eigenmodes requires special physics or a common property driven by instability. Previous investigations have focused exclusively on in the core tokamak discharges. The here apply wide range physical mechanisms instability, turbulent mode coupling, and parameter regimes, with modeling feature that has been reduced two-field description. All regimes which...

Zonal flows are shown to regulate ion temperature gradient turbulence by enabling efficient energy transfer from the instability a damped eigenmode in unstable wavenumber range. The mode also saturates when zonal not active saturation dynamics, for example, electron turbulence, but stable is less and requires larger amplitude balance drive. From numerical solutions of fluid model with single eigenmode, an decomposition nonlinear evolution shows that dominant involves triplet correlation...

We study the process of magnetic reconnection in a coalescing island setup by means numerical simulation. This mimics flux tube merging which can take place solar corona, laboratory, and astrophysical objects. Simulations are performed with magnetohydrodynamics (MHD), Hall-MHD, newly developed Coupled MHD Particle-In-Cell (PIC) model (CMAP). treats global simulation domain MHD, while region around zone is treated PIC. CMAP code allows us to simulate larger-scale domains lesser computing...

Energy transfer to damped modes in gyrokinetic ion temperature gradient driven turbulence is studied understand the dynamics and find scaling representations for heavily populated mode space. Proper orthogonal linear eigenmode decompositions are introduced examined assess whether well-resolved what scales they encompass. It observed that across a range of inhomogeneous receive energy simultaneously directly from unstable mode, constituting form parallel transfer, distinct serial mode-to-mode...

We simulate decaying turbulence in electron-positron pair plasmas using a fully-kinetic particle-in-cell (PIC) code. run two simulations with moderate-to-low plasma β (the ratio of thermal pressure to magnetic pressure). The energy decay rate is found be similar both cases. perpendicular wave-number spectrum shows slope between and , where the (⊥) parallel (∥) directions are defined respect field. particle kinetic distribution function formation non-thermal feature case lower β, close E−1....

We present simulations of magnetic reconnection with a newly developed coupled MHD-PIC code. In this work global magnetohydrodynamic (MHD) simulation receives kinetic feedback within an embedded region that is modeled by particle-in-cell (PIC) The PIC code initial and boundary conditions from the MHD simulation, while solution updated state. briefly describe coupling mechanism. This method suitable for simulating problems, as we show example in coalescence islands. compare MHD, Hall-MHD,...

We perform 2.5D particle-in-cell simulations of decaying turbulence in the presence a guide (out-of-plane) background magnetic field. The fluctuating field initially consists Fourier modes at low wavenumbers (long wavelengths). With time, electromagnetic energy is converted to plasma kinetic (bulk flow+thermal energy) rate per unit volume ${\pp J}\cdot{\pp E}$ for current density J}$ and electric E}$. Such well known evolve toward state with strongly intermittent current. Here we decompose...

We simulate decaying turbulence in electron-positron pair plasmas using a fully- kinetic particle-in-cell (PIC) code. run two simulations with moderate-to-low plasma beta. The energy decay rate is found to be similar both the cases. perpendicular wave-number spectrum of magnetic shows slope k^-1.3 particle distribution function formation non-thermal feature case lower beta, close E^-1. role thin turbulent current sheets this process investigated. heating by E_{\parallel}.J_{\parallel} term...

Kinetic Alfvén waves (KAWs) are simulated with a 3D particle-in-cell (PIC) code by using the eigenvector relations of density, velocity, electric, and magnetic field fluctuations derived from two-fluid KAW model. Similar simulations also performed whistler setup. The 2D converted into rotation reference frame. initial condition for is superposition several at scales slightly larger than ion skin depth. nonlinear interactions produce transfer energy to smaller scales. perturbation ratios,...

We investigate reconnection of magnetic field lines in sheared configurations due to fluctuations driven by random forcing means numerical simulations. The simulations are performed with an incompressible, pseudo-spectral magnetohydrodynamics code 2D where we take thick, resistively decaying, current-sheet like which do not reconnect spontaneously. describe and test the that is introduced momentum equation drive fluctuations. It found does change rate decay; however, it adds removes energy...