Numerical-experimental investigation of the enhancement of the electromagnetic ion cyclotron instability by cold plasma

The theoretical prediction of the enhancement of the maximum growth rate of the electromagnetic ion cyclotron instability, occurring in thermally anisotropic plasmas, in the presence of a cold plasma component was investigated by a computer simulation experiment. The plasma parameters used are βp ≡ 8πnp,wkT∥,p/B0² = 1 and kT∥,p = 25 keV. Three relevant cases were considered: case I, pure warm (np,c = 0) isotropic (Ap ≡ T⊥,p/T∥,p − 1 = 0) plasma; case II, pure warm (np,c = 0) anisotropic (Ap = 0.5) plasma; and case III, a mixed warm-cold (np,c/np,w = 2) anisotropic (Ap = 0.5) plasma system. The results of the investigation confirm the linear theory of the enhancement of the instability. Moreover, they show the evolution of the unstable plasma systems through their quasi-linear and nonlinear stages. These results are relevant for active magnetospheric experiments to be performed in the near future.