Inertial Alfvén waves in auroral acceleration region with H+, He+ and O+ ions plasma

Abstract

The propagation of inertial Alfven wave is investigated in cold, low- $\beta $ , homogeneous and bi-Maxwellian plasma consisting of multi-ions (H+, He+ and O+). Kinetic approach is adopted to derive the dispersion relation, damping rate, group velocity and growth/ damping length of the wave. Figures are exhibited with respect to ${ck_{\bot }} / {\omega _{pe}}$ . Effects of density variation with multi-ions are analysed on frequency, damping rate, parallel and perpendicular components of group velocity and growth/ damping length of the inertial Alfven wave. It is found that varying densities of multi-ions significantly influence the frequency, damping rate and group velocity of inertial Alfven wave. The wave frequency is observed between 0.5 to $18~\mbox{s}^{- 1}$ pertaining to observational data. The increasing density of heavy ions reduces the frequency of waves. The presence of He+ and O+ enhances the damping of wave showing more transfer of energy from wave to particles leading to increase in electron acceleration. The order of parallel and perpendicular group velocity is found to be $10^{9}~\mbox{cm}/\mbox{s}$ and $10^{5}~\mbox{cm}/\mbox{s}$ respectively. Maximum perpendicular growth length is observed corresponding to the minimum damping rate of wave at ${ck_{\bot }} / {\omega _{pe}} <1$ , signifying the dynamics in transverse direction to the magnetic field which are more significant in the present analysis. The parameters relevant to auroral acceleration region are used for graphical analysis. The applications of present study may be towards the electron acceleration in the dynamics of auroral acceleration region consisting of heavy ions in background plasma.