Electromagnetic direct implicit plasma simulation
A 2D electromagnetic version of the direct implicit PIC algorithm has been developed and implemented in the new code AVANTI. The code has been tested on electron beam filamentation and magnetic reconnection problems and has fulfilled most of the promise of implicit PIC. It runs stably with an arbitrarily large time step and is quite robust with respect to large particle fluctuations that result when plasmas are represented with small numbers of particles per cell N/sub c/. Several numerical obstacles were overcome during the development of the AVANTI. A method of determining the implicit susceptibility chi is described which allows the code to avoid a nonlinear instability associated with small N/sub c/. We find a form of ''simplified differencing'' that provides a very robust algorithm without need for explicit smoothing. Another hurdle is the solution of the EM field equations. If the collisionless skin depth is not well resolved in high density regions, the terms containing the tensor chi dominate the E field equation and strongly couple the components. This strong coupling is handled by simultaneous solution of these equations: generalizing to simultaneous splitting in 2D. In regions where the skin depth is well resolved, terms associated with purely electromagnetic waves dominate but do not fit symmetrically into the simultaneous splitting scheme. Introducing the electrostatic potential, the troublesome asymmetric electrostatic part of E cancels but requires a fourth equation for phi to be solved simultaneously along with the three E components. Finally, extension and generalization of the conventional explicit PIC divergence correction step, necessary to maintain Gauss' law, is needed.
- Research Organization:
- Physics Department, Lawrence Livermore National Laboratory, University of California, Livermore, California 94550
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 6199562
- Journal Information:
- J. Comput. Phys.; (United States), Vol. 72:1
- Country of Publication:
- United States
- Language:
- English
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