60 research outputs found
The Energy Conserving Particle-in-Cell Method
A new Particle-in-Cell (PIC) method, that conserves energy exactly, is
presented. The particle equations of motion and the Maxwell's equations are
differenced implicitly in time by the midpoint rule and solved concurrently by
a Jacobian-free Newton Krylov (JFNK) solver. Several tests show that the finite
grid instability is eliminated in energy conserving PIC simulations, and the
method correctly describes the two-stream and Weibel instabilities, conserving
exactly the total energy. The computational time of the energy conserving PIC
method increases linearly with the number of particles, and it is rather
insensitive to the number of grid points and time step. The kinetic enslavement
technique can be effectively used to reduce the problem matrix size and the
number of JFNK solver iterations
Multi-GPU Acceleration of the iPIC3D Implicit Particle-in-Cell Code
iPIC3D is a widely used massively parallel Particle-in-Cell code for the
simulation of space plasmas. However, its current implementation does not
support execution on multiple GPUs. In this paper, we describe the porting of
iPIC3D particle mover to GPUs and the optimization steps to increase the
performance and parallel scaling on multiple GPUs. We analyze the strong
scaling of the mover on two GPU clusters and evaluate its performance and
acceleration. The optimized GPU version which uses pinned memory and
asynchronous data prefetching outperform their corresponding CPU versions by
5-10x on two different systems equipped with NVIDIA K80 and V100 GPUs.Comment: Accepted for publication in ICCS 201
Collisionless magnetic reconnection in a plasmoid chain
The kinetic features of plasmoid chain formation and evolution are
investigated by two dimensional Particle-in-Cell simulations. Magnetic
reconnection is initiated in multiple X points by the tearing instability.
Plasmoids form and grow in size by continuously coalescing. Each chain plasmoid
exhibits a strong out-of plane core magnetic field and an out-of-plane electron
current that drives the coalescing process. The disappearance of the X points
in the coalescence process are due to anti-reconnection, a magnetic
reconnection where the plasma inflow and outflow are reversed with respect to
the original reconnection flow pattern. Anti-reconnection is characterized by
the Hall magnetic field quadrupole signature. Two new kinetic features, not
reported by previous studies of plasmoid chain evolution, are here revealed.
First, intense electric fields develop in-plane normally to the separatrices
and drive the ion dynamics in the plasmoids. Second, several bipolar electric
field structures are localized in proximity of the plasmoid chain. The analysis
of the electron distribution function and phase space reveals the presence of
counter-streaming electron beams, unstable to the two stream instability, and
phase space electron holes along the reconnection separatrices.Comment: accepted for publication in special issue "Magnetic reconnection and
turbulence in space, laboratory and astrophysical systems" of Nonlinear
Processes in Geophysic
PICPANTHER: A simple, concise implementation of the relativistic moment implicit Particle-in-Cell method
A three-dimensional, parallelized implementation of the electromagnetic
relativistic moment implicit particle-in-cell method in Cartesian geometry
(Noguchi et. al., 2007) is presented. Particular care was taken to keep the
C++11 codebase simple, concise, and approachable. GMRES is used as a field
solver and during the Newton-Krylov iteration of the particle pusher. Drifting
Maxwellian problem setups are available while more complex simulations can be
implemented easily. Several test runs are described and the code's numerical
and computational performance is examined. Weak scaling on the SuperMUC system
is discussed and found suitable for large-scale production runs.Comment: 29 pages, 8 figure
Variational Formulation of Macro-Particle Models for Electromagnetic Plasma Simulations
A variational method is used to derive a self-consistent macro-particle model
for relativistic electromagnetic kinetic plasma simulations. Extending earlier
work [E. G. Evstatiev and B. A. Shadwick, J. Comput. Phys., vol. 245, pp.
376-398, 2013], the discretization of the electromagnetic Low Lagrangian is
performed via a reduction of the phase-space distribution function onto a
collection of finite-sized macro-particles of arbitrary shape and
discretization of field quantities onto a spatial grid. This approach may be
used with both lab frame coordinates or moving window coordinates; the latter
can greatly improve computational efficiency for studying some types of
laser-plasma interactions. The primary advantage of the variational approach is
the preservation of Lagrangian symmetries, which in our case leads to energy
conservation and thus avoids difficulties with grid heating. Additionally, this
approach decouples particle size from grid spacing and relaxes restrictions on
particle shape, leading to low numerical noise. The variational approach also
guarantees consistent approximations in the equations of motion and is amenable
to higher order methods in both space and time. We restrict our attention to
the 1-1/2 dimensional case (one coordinate and two momenta). Simulations are
performed with the new models and demonstrate energy conservation and low
noise.Comment: IEEE Transaction on Plasma Science (TPS) Special Issue: Plenary and
Invited Papers of the Pulsed Power and Plasma Science Conference (PPPS 2013
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