The Alfvéen IonCyclotron Instability: Simulation Theory and Techniques
Abstract
The numerical properties of a particleion, fluidelectron computer simulation code, used in the study of the parallelpropagating electromagnetic Alfven ioncyclotron (AIC) instability, are examined. A numerical oddeven mode is suppressed by means of a twotimestep averaging method. Excellent energy conservation is obtained by using a method similar to the Boris particle mover to advance the transverse fields. Linear growth rates obtained' from the code differ substantially from those predicted by uniform Vlasov theory, here derived using a muitifluid model. Short wavelengths in particular show substantial growth rates when damping is predicted, and additionally show strong linear mode coupling. Positive growth rates are even observed in the case of a Maxwellian ion distribution. Disagreement is also generally found among shortwavelength mode frequencies. These inconsistencies are resolved by taking into consideration general grid and discreteparticle effects of the simulation model. A theoretical study reveals a real, physical process by which an ion distribution may collisionlessly relax via shortwavelength AIC instabilities acting resonantly on small portions of the distribution function. This process is combined with a linear mode coupling theory and other characteristics of the AIC instability to explain all observed differences. Nonlinear shortwavelength saturation levels are also obtained and their relevance to other fieldaligned, electromagnetic simulations is discussed.
 Publication:

Journal of Computational Physics
 Pub Date:
 October 1988
 DOI:
 10.1016/00219991(88)900496
 Bibcode:
 1988JCoPh..78..251O
 Keywords:

 Computerized Simulation;
 Ion Cyclotron Radiation;
 Magnetohydrodynamic Stability;
 Conducting Fluids;
 Ion Distribution;
 Normal Density Functions;
 PlasmaParticle Interactions;
 Vlasov Equations;
 Plasma Physics