Quantitative comparison of reduced-description particle-in-cell and quasilinear-Zakharov models for parametrically excited Langmuir turbulence

The effect of kinetic processes on the saturation of parametric instabiliti es in an electromagnetically driven plasma is investigated. A reduced-descr iption particle-in-cell technique is used as a benchmark to test a new quas ilinear-Zakharov model which accounts for electron heating due to Landau da mping by coupling the quasilinear diffusion equation to the Zakharov equati ons. The reduced-description particle-in-cell method utilizes a two-time-sc ale approximation which significantly reduces the numerical dissipation and ion noise levels. This approach allows accurate modeling of Langmuir and i on acoustic waves in regimes typically studied with Zakharov simulations. T he comparison of the two models is performed for the test case of a one-dim ensional homogeneous plasma driven by a spatially uniform pump in both the Langmuir decay instability cascade and collapse regimes. Good agreement is found in both weakly and strongly driven regimes for the total Langmuir wav e energy and evolved electron velocity distributions. Electron heating sign ificantly decreases saturation levels in strongly driven regimes by increas ing the Landau damping rate, bringing the quasilinear-Zakharov simulations in much closer agreement with the reduced-description particle-in-cell simu lations than standard Zakharov simulations, which do not account for the ev olution of the electron distribution. (C) 2000 American Institute of Physic s. [S1070-664X(00)01907-8].