Persistence of Precursor Waves in Two-dimensional Relativistic Shocks

Abstract

We investigated the efficiency of coherent upstream large-amplitude electromagnetic wave emission via synchrotron maser instability at relativistic magnetized shocks by using two-dimensional particle-in-cell simulations. We considered the purely perpendicular shock in an electron-positron plasma. The coherent wave emission efficiency was measured as a function of the magnetization parameter σ, which is defined by the ratio of the Poynting flux to the kinetic energy flux. The wave amplitude was systematically smaller than that observed in one-dimensional simulations. However, it continued to persist, even at a considerably low magnetization rate, where the Weibel instability dominated the shock transition. The emitted electromagnetic waves were sufficiently strong to disturb the upstream medium, and transverse filamentary density structures of substantial amplitude were produced. Based on this result, we discuss the possibility of the wakefield acceleration model for the production of non-thermal electrons in a relativistic magnetized ion-electron shock.

Precursor Wave Amplification by Ion–Electron Coupling through Wakefield in Relativistic Shocks

“…We performed 1D ion-electron shock simulations for comparison and the results are shown in blue. The wave energy in 2D is systematically smaller than that in 1D because of the inhomogeneity along the shock surface (Iwamoto et al 2017(Iwamoto et al , 2018.…”

“…Recently, our high-resolution two-dimensional (2D) PIC simulations in pair plasmas (Iwamoto et al 2017(Iwamoto et al , 2018 showed that the wave emission continues even well after Weibel instability (Weibel 1959;Fried 1959) becomes active at the shock front. The precursor waves are large enough to disturb the upstream plasma and induces transverse density filaments extended well ahead of the shock front (see also Plotnikov et al 2018).…”

Constraints on the engines of fast radio bursts

“…Larmor rotation of charges entering the shock and gyrating around the ordered magnetic field creates the necessary population inversion in the form of an unstable ring-like particle distribution function, which relaxes by transferring energy into an outwardly propagating coherent electromagnetic wave (e.g. Gallant et al 1992;Hoshino et al 1992;Amato & Arons 2006;Hoshino 2008;Sironi & Spitkovsky 2009Iwamoto et al 2017Iwamoto et al , 2018Plotnikov & Sironi 2019).…”

The baryon loading effect on relativistic astrophysical jet transport in the interstellar medium

“…This also implies that the single-zone model [59] (commonly adopted in the jet emission calculation) may only suitable for leptonic jets. Moreover, apart from the diffusive shock acceleration [ [60][61][62], this acceleration at the leading edge of the relativistic jet may serve as another mechanism in generating the ultra-high-energy cosmic ray (UHECR) [58,63].…”