Excitation of nonlinear ion acoustic waves in CH plasmas

Abstract

Excitation of nonlinear ion acoustic wave (IAW) by an external electric field is demonstrated by Vlasov simulation. The frequency calculated by the dispersion relation with no damping is verified much closer to the resonance frequency of the small-amplitude nonlinear IAW than that calculated by the linear dispersion relation. When the wave number kλ De increases, the linear Landau damping of the fast mode (its phase velocity is greater than any ion's thermal velocity) increases obviously in the region of T i /T e < 0.2 in which the fast mode is weakly damped mode. As a result, the deviation between the frequency calculated by the linear dispersion relation and that by the dispersion relation with no damping becomes larger with kλ De increasing. When kλ De is not large, such as kλ De = 0.1, 0.3, 0.5, the nonlinear IAW can be excited by the driver with the linear frequency of the modes. However, when kλ De is large, such as kλ De = 0.7, the linear frequency can not be applied to exciting the nonlinear IAW, while the frequency calculated by the dispersion relation with no damping can be applied to exciting the nonlinear IAW.

Harmonic effects on ion-bulk waves and simulation of stimulated ion-bulk-wave scattering in CH plasmas

“…Therefore, the nature of lower frequency waves with v φ ≃ v ti is not understood due to a strong Landau damping, which is similar to the electron-acoustic waves (EAWs) [4]. By adding a external driving electric field (driver), after several bounce time of particles, the Landau damping of IBk waves will be decreased and be nearly zero [5][6][7] due to particles trapping. However, the energy was stored in the nonlinear IBk waves only when the wave number k was larger than a special value [2], which has not been explained and calls for a clear interpretation.…”

“…Assuming that the electron temperature equals T e and the same temperature of all ions equals T i , the dispersion relation of the infinitesimal amplitude IBk waves in non-magnetized, homogeneous plasmas consisting of multi-ion species is given by [7] Re(ǫ L (Re(ω), k)) = 0,…”

“…As we know, there is a nonlinear frequency shift (NFS) of the large amplitude BGK modes [16] due to particles trapping and harmonic generation, such as the nonlinear IAWs [7,[26][27][28], Langmuir waves (LWs) [18], and nonlinear electron acoustic waves (EAWs) [4]. To obtain the resonance curves as shown in Figs.…”

Growth rate and gain of stimulated Brillouin scattering considering nonlinear Landau damping due to particle trapping

“…Thus, the wave number of IAW excited by backward SBS is k A λ De ≃ 2k 0 = 2 vte c n c /n e − 1, where k 0 is the wave number of pump light, v te = T e /m e is the electron thermal velocity, n e , T e , m e are the density, temperature and mass of the electron. Assuming fully ionized, neutral, unmagnetized plasmas, the linear dispersion relation of the ion acoustic wave in multi-ion species plasmas is given by [20][21][22] ǫ(ω, k = k A ) = 1 + j χ j = 0,where χ j is the susceptibility of particle j (j = e, H, C).And ω = Re(ω) + i * Im(ω) is complex frequency. Re(ω) and Im(ω) are the frequency and Landau damping of IAW.…”

Burst behavior due to the quasimode excited by stimulated Brillouin scattering in high-intensity laser–plasma interactions

“…where v te = T e /m e is the electron thermal velocity, n e , T e , m e is the density, temperature and mass of the electron. Considering fully ionized, neutral, unmagnetized plasmas with the same temperature of all ion species (T H = T C = T i ), the linear dispersion relation of the ion acoustic wave in multi-ion species plasmas is given by [14][15][16]…”