A rigorous theoretical investigation of linear dust ion acoustic (DIA) solitary waves in an unmagnetized complex plasma consisting of ion and ion beam fluids, nonthermal electrons that are Cairns distributed and immobile dust particles were undertaken. It was found out that, for large beam speeds, three stable modes propagated as solitary waves in the beam plasma. These were the "Fast", "Slow" and "Ion-acoustic" modes. For two stream instability to occur between ion and ion beam, it is shown that ( ) 3 i k ω σ → or when ( ) 0 3 b b k u ω σ − → .

Ion-acoustic solitary (IAS) waves in electron-positron-ion (e-p-i) plasma have been of interest to many researchers probably due to their relevance in understanding the Universe. However, the study of non-linear ion-acoustic waves in e-p-i plasma with non-thermal electrons has not been adequately studied. A theoretical investigation on non-linear IAS waves in e-p-i plasma comprising of warm inertial adiabatic fluid ions and electrons that are kappa distributed, and Boltzman distributed positron is presented here using the Sagdeev potential technique. It was found that existence domains of finite amplitude IAS waves were confined within the limits of minimum and maximum Mach numbers with varying κ values. For lower values of κ , the amplitude of the solitary electrostatic potential structures increased as the width decreased, while for high values, the potential amplitude decreased as the width of the solitary structure increased.

In this paper, we present a complete structure of a quasi-Keplerian thin accretion disc with an internal dynamo around a magnetized neutron star. We assume a full quasi-Keplerian disc with the azimuthal velocity deviating from the Keplerian fashion by a factor ξ (0 < ξ < 2). In our approach, we vertically integrate the radial component of the momentum equation to obtain the radial pressure gradient equation for a thin quasi-Keplerian accretion disc. Our results show that at large radial distance the accretion disc behaves in a Keplerian fashion. But, close to the neutron star, pressure gradient force (PGF) largely modifies the disc structure resulting into sudden dynamical changes in the accretion disc. The corotation radius is shifted inwards (outwards) for ξ > 1 (for ξ < 1) and the position of the inner edge with respect to the new corotation radius is also relocated accordingly as compared to the Keplerian model. The resulting PGF torque couples with viscous torque (when ξ < 1) to provide a spin-down torque and a spin-up torque (when ξ > 1) while in the advective state. Therefore, neglecting the PGF is a big omission as has been the case in previous models. This result has the potential of explaining the observable dynamic consequences of accretion discs around magnetized neutron stars.