Role of halo electrons on the evolution of combined wave-spectrum of electron-ion mirror instability in the solar wind

Abstract Modern spacecraft missions reveal the decomposed form of electrons in the expanding solar wind. Non-thermal features in the form of temperature anisotropy ignite the various instabilities and define the dynamics of plasma systems. In the rare-collisions scenario, such instabilities play a dominant role to keep thermodynamic equilibrium states of charge particles. The dispersion characteristics (growth rate and instability domain) of purely growing ( ω r = 0) combined electron-ion mirror instability in the linear and quasilinear phases of instability evolution are presented. Mirror instability appears for large perpendicular temperature condition i.e. T ⊥ > T ‖ in the relatively high plasma beta regimes. Based on in situ measurements, we assume bi-Maxwellian forms of ions, core and halo electrons components in which the initial temperatures are allowed to vary in time t . Employing a moment-based quasilinear theory, a set of self-consistent equations have been derived which comprised dispersion relation, dynamical temperatures relations, and wave-energy density equation. During the time-evolution of combined electron-ion mirror instability, the growth rate keeps falling and associated wave-energy density rises concomitantly. Initial large temperature anisotropy ratio of ions, core and halo electrons favor the relaxation/saturation of initial distribution and wave-intensity due to more available free energy for the peak growth rate/wave-energy density. Further, a time variation in the halo electrons population in the radially expanding solar wind put a notable impact on combined ions-electrons instability evolution. Higher values of halo electrons density favors growth rate, wave-energy density, and an early relaxation of ions and electron distribution.