Self-consistency vanishes in the plateau regime of the bump-on-tail instability

TL;DR

This paper demonstrates that in the broad plateau regime of the bump-on-tail instability, self-consistency effects disappear, challenging the conventional link between growth rate renormalization and the timescale separation in plasma turbulence.

Contribution

It reveals that self-consistency vanishes in the plateau regime, providing new insights into the dynamics of the bump-on-tail instability beyond the turbulent trapping approximation.

Findings

Self-consistency vanishes in broad plateau regimes.

Contrasts with the turbulent trapping Ansatz.

Challenges the link between growth rate renormalization and timescale separation.

Abstract

Using the Vlasov-wave formalism, it is shown that self-consistency vanishes in the plateau regime of the bump-on-tail instability if the plateau is broad enough. This shows that, in contrast with the "turbulent trapping" Ansatz, a renormalization of the Landau growth rate or of the quasilinear diffusion coefficient is not necessarily related to the limit where the Landau growth time becomes large with respect to the time of spreading of the particle positions due to velocity diffusion.