Quasilinear approach to bump-on-tail instability using non-Maxwellian distributions

Abstract

Abstract Spacecraft observations provide evidence about the existence of various waves and kinetic instabilities in solar wind plasmas. These instabilities and waves play an important role in the dynamics of the solar wind. In the present work, bump-on-tail (BOT) instability is revisited by employing the κ and then the modified (r, κ) distributions using a quasilinear approach. The evolution of bump-on-tail instability is studied analytically and numerically by using the solar wind data. The growth rate of BOT instability for varying ratios of temperature and number density is also observed. It is observed that the maximum growth rate increases with increasing number density and decreases with increasing electron temperature in the bump. The effect of spectral indices κ in the kappa distribution and r and κ in the modified (r, κ) distribution functions ultimately contributes towards the shoulder and tail of the distribution functions and the results appear to have been modified. Stimulation of wave energy density shows rapid variation in the quasilinear evolution of bump-on-tail instability as compared to the simple linear model.