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

Abstract

The propagation of inertial Alfvén wave is investigated in cold, low-β, 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 ⊥ /ω 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 Alfvén wave. It is found that varying densities of multi-ions significantly influence the frequency, damping rate and group velocity of inertial Alfvén wave. The wave frequency is observed between 0.5 to 18 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 cm/s and 10 5 cm/s respectively. Maximum perpendicular growth length is observed corresponding to the minimum damping rate of wave at ck ⊥ /ω 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.

The effect of heavy ions on the dispersion properties of kinetic Alfvén waves in astrophysical plasmas

“…We also observe a small wave number domain where the mode becomes slightly damped -a phenomenon that is not present in the first case. This increased damping due to the presence of O + (or other heavy ions) has been previously observed by Tamrakar et al (2019) and associated with particle energization by the waves. Consistently with recent results (Moya et al 2021), Alfvénic waves in a plasma infused with heavy ions acquire positive polarization in a wave number domain that grows with the propagation angle.…”

“…Kinetic Alfvén waves (KAWs) are Alfvénic waves that propagate at large wave-normal angles, when the mode turns compressive and develops a large parallel electric field due to kinetic effects, which give this mode its name. These characteristic kinetic effects become relevant under two conditions in typical electron-proton plasma: 1) in the hot electron case (β > m e /m p ) as the perpendicular wavelength reaches the order of the scale of the protons' gyroradius (Hasegawa 1977;Gary 1986;Hollweg 1999) and 2) in the cold electron case (β < m e /m p ) as it reaches the electron's inertial length (Goertz & Boswell 1979;Lysak & Lotko 1996;Tamrakar et al 2019;Lysak 2023). In this latter case, the waves can also be referred to as inertial Alfvén waves (de Assis et al 2020).…”

Self‐organization of earth's inner magnetospheric multi‐ion plasma

“…[1][2][3][4][5] In recent years, extensive research has been conducted on multi-ion plasmas in order to investigate various nonlinear structures. For instance, several researchers have studied ion cyclotron waves, [6][7][8][9][10] kinetic Alfvén waves, [11][12][13][14][15] electrostatic ion-cyclotron waves, [16] inertial Alfvén waves, [17] and oscillitons [18] in multi-ion plasmas containing three positive ion species that occur in various regions of the earth's magnetosphere.…”