Ion-acoustic super rogue waves in ultracold neutral plasmas with nonthermal electrons

Abstract

The ion-acoustic rogue waves in ultracold neutral plasmas consisting of ion fluid and nonthermal electrons are reported. A reductive perturbation method is used to obtain a nonlinear Schrödinger equation for describing the system and the modulation instability of the ion-acoustic wave is analyzed. The critical wave number kc, which indicates where the modulational instability sets in, has been determined. Moreover, the possible region for the ion-acoustic rogue waves to exist is defined precisely. The effects of the nonthermal parameter β and the ions effective temperature ratio σ∗ on the critical wave number kc are studied. It is found that there are two critical wave numbers in our plasma system. For low wave number, increasing β would lead to cringe kc until β approaches to its critical value βc, then further increase of β beyond βc would enhance the values of kc. For large wave numbers, the increase of β would lead to a decrease of kc. However, increasing σ∗ would lead to the reduction of kc for all values of the wave number. The dependence of the rogue waves profile on the plasma parameters is numerically examined. It is found that the rogue wave amplitudes have complex behavior with increasing β. Furthermore, the enhancement of σ∗ and the carrier wave number k reduces the rogue wave amplitude. It is noticed that near to the critical wave number, the rogue wave amplitude becomes high, but it shrinks whenever we stepped away from kc. The implications of our results in laboratory ultracold neutral plasma experiments are briefly discussed.