In this paper, the instability of electrostatic twisted modes carrying orbital angular momentum in the moving electron–positron–ion plasma is investigated. In the kinetic theory approach, the general dispersion relation of twisted modes is derived by using Laguerre–Gaussian perturbed distribution function and electrostatic potential in the paraxial limit. Utilizing the obtained general dispersion relation for a specific case of electron–positron (e–p) shell with temperature anisotropy interacted with moving ion background, the effects of angular mode number, electrons and positrons temperature, and positron concentration on the group velocity and instability growth rate of twisted waves are illustrated, numerically. The results of the present investigation will greatly attribute to the understanding of e–p jet dynamic in astrophysical environments and laboratory experiments where the twisted modes can play a central role as a perturbed term.

The transmitted and reflected second harmonics (SH) generation by an oblique p-polarized laser pulse irradiated on vacuum-magnetized plasma interface is investigated. The laser pulse propagates through a homogenous, underdense, and transversely magnetized plasma. The transverse magnetic field plays the role of a self-generated magnetic field produced in laser plasma interaction. It is shown that if the transmitted and reflected SH components investigated as a simultaneous process, the maximum SH power deviates from previous reports specially near the critical angle. The deviation increases with laser field intensity and plasma density. The results reveal that the conversion efficiency increases slightly by increasing incident angle and drastically enhances near the critical angle. We show that the transmitted SH power decreases by increasing the magnetic field strength, in contrast to the normal incidence, which the SH power is increased. The comparison revealed that the SH efficiency is greater for transmitted component, while the reflected component is more proper for technical and experimental applications. This paper not only conforms the previous reports for angle far from the critical but also modifies them for the SH generation near the critical angle. Moreover, this paper gives a new insight for SH generation by a magnetized plasma.