Ion-acoustic waves in dense magneto-rotating quantum plasma

A theoretical study is presented for the oblique propagation of linear and nonlinear ion acoustic waves in a dense electron-ion quantum plasma, as that found in dense astrophysical objects like white dwarfs, rotating around an axis at an angle θ with the direction of the constant magnetic field $B→=B0ẑ$⁠. In the absence of exact analytical solutions, we look for approximate ones by applying different approximation techniques like linearization, reductive perturbation, phase portraits, etc. The linear dispersion relation, obtained as a quadratic equation in the plasma frequency ω², reveals interesting features. The small amplitude analysis for the nonlinear waves, using the reductive perturbation technique, yields the Korteweg–de Vries equation, whose solutions are solitary waves. The effects of various physical parameters like speed and angle of rotation, strength of the magnetic field, the quantum diffraction term, etc., on the shape of the nonlinear structures, are investigated numerically. It is observed that the different plasma parameters have similar effects on both small and arbitrary amplitude waves—stronger magnetic field, larger quantum effects, and higher speed of rotation decrease their width. Furthermore, as the angle between the rotation axis and magnetic axis decreases, i.e., the rotation is aligned with the direction of the magnetic field, the waves get sharper. Additionally, the energy of the small amplitude solitary wave decreases with an increase in the speed of rotation and stronger quantum effects.