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

Abstract

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