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.

► We develop a particle-in-cell method that conserves exactly the energy not only in the limit of vanishing time step, but with finite time step also. ► The energy conserving particle-in-cell method is fully implicit. ► The finite grid instability is eliminated in the energy conserving particle-in-cell method. ► The kinetic enslavement technique is used to reduce the problem matrix size.