Velocity moment-based quasilinear theory and particle-in-cell simulation of parallel electron firehose instability

The present paper investigates the physics of electron firehose instability propagating parallel to the direction of ambient magnetic field vector, by means of particle-in-cell simulation and macroscopic quasilinear kinetic theory. The electron firehose instability is excited when parallel electron temperature exceeds perpendicular temperature, T-parallel to e > T-perpendicular to e, under high beta conditions. A recent paper [Sarfraz et al., Phys. Plasmas 24, 012907 (2017)] formulated the quasilinear theory of parallel electron firehose instability by assuming that the electron and proton velocity distribution functions can be approximately described by bi-Maxwellian forms for all times but allowing for dynamical changes in perpendicular and parallel temperatures as well as the wave intensity. The present paper examines the validity of such an approach by making direct comparison against particle- in-cell simulation. It is shown that the macroscopic quasilinear approach provides a qualitative description of the nonlinear phase of the instability, but some quantitative discrepancies are also found. Possible causes for the discrepancies are discussed. Published by AIP Publishing.