CHARGE CONSERVATION IN ELECTROMAGNETIC PIC CODES - SPECTRAL COMPARISON OF BORIS DADI AND LANGDON-MARDER METHODS/

Non-charge conserving current collection algorithms for electromagneti c PIC plasma simulations may cause errors in Gauss's law. These errors arise from violations of the charge continuity equation, del . J = -p artial derivative rho/partial derivative t, which in turn cause errors in the irrotational part of E. Two techniques for reducing these erro rs are examined and compared: a modified Marder correction which corre cts electric fields locally and primarily affects short wavelengths, a nd a Boris divergence correction, which solves Poisson's equation to c orrect the electric fields so that Gauss's law is enforced globally. T he effect of each method on the spectrum of the error is examined. Com putational efficiency and accuracy of the two techniques are compared: neither method is clearly superior. Cases examined include correction s in electromagnetic relativistic beam simulations, and a hot thermal plasma. In addition, the spectral comparison provides insight into the behavior of the schemes applied. (C) 1997 Elsevier Science B.V.