Quasilinear analysis of saturation properties of broadband whistler mode waves

Abstract

Abstract Saturation properties of parallel propagating broadband whistler mode waves are investigated using quasilinear theory. By assuming that the electron distribution stays bi‐Maxwellian, we combine the previously obtained energy equation of quasilinear theory with wave equation to self‐consistently model the excitation of broadband whistler waves. The resulting evolution profile of wave intensity, spectrum, and electron temperature are consistent with those from particle‐in‐cell (PIC) simulations. We obtain the inverse relation between the saturation temperature anisotropy ( A ) and parallel plasma beta ( β ∥ ) directly from quasilinear theory. Our A ‐ β ∥ relation agrees very well with previous results from observation and PIC simulation. We also demonstrate that it might be possible to predict the wave amplitude from the initial maximum linear growth rate alone and show that the peak frequency and spectrum width are well‐defined functions of the final β ∥ at saturation, but not of the initial β ∥ .