Electrostatic modes in multi-ion and pair-ion collisional plasmas

Abstract

The physics of plasmas containing positive and negative ions is discussed with special attention to the recently produced pair-ion plasma containing ions of equal mass and opposite charge. The effects of the density gradient in the direction perpendicular to the ambient magnetic field vector are discussed. The possible presence of electrons is discussed in the context of plasma modes propagating at an angle with respect to the magnetic field vector. It is shown that the electron plasma mode may become a backward mode in the presence of a density gradient, and this behavior may be controlled either by the electron number density or the mode number in the perpendicular direction. In plasmas with hot electrons an instability may develop, driven by the combination of electron collisions and the density gradient, and in the regime of a sound ions' response. In the case of a pure pair-ion plasma, for lower frequencies and for parameters close to those used in the recent experiments, the perturbed ions may feel the effects of the magnetic field. In this case the plasma mode also becomes backward, resembling features of an experimentally observed but yet unexplained backward mode.

Drift waves and counter rotating vortices in pair-ion plasmas

“…Hasegawa-Mima (HM) equation for drift waves in pair-ion-electron plasma has also been discussed. Recently, Vranjes et al [12] have studied the pair-ion plasma in the presence of electrons and discussed that the electron plasma mode can become a backward mode in the presence of density gradients. They have also explained some mechanisms, which can be responsible for the presence of electrons in the pair-ion plasma system.…”

Relaxed magnetic field structures in multi-ion plasmas

“…The multi-ion plasmas have been studied extensively to investigate different modes such as nonlinear Alfvén waves (Faria et al 1998), acoustic solitary waves (Verheest et al 2008), solitons (Sauer et al 2001) and electrostatic modes (Vranjes et al 2008).…”

Shear flow-driven electrostatic instabilities in low density and low temperature pair-ion plasmas with and without electrons

“…16 The effects of collisions have been considered in Ref. 17 and it has been argued that even if the magnetic filtering is reliable as mentioned in Ref. 1, electrons can be produced as a result of collisions between positive and negative ions.…”