Kinetic turbulence in relativistic plasma: from thermal bath to non-thermal continuum

TL;DR

This study uses particle-in-cell simulations to explore turbulence in relativistic pair plasma, revealing classical and steeper magnetic spectra and a non-thermal particle energy distribution, with implications for astrophysical high-energy phenomena.

Contribution

It provides new insights into the spectral properties and particle acceleration mechanisms in relativistic plasma turbulence through detailed simulations.

Findings

Magnetic energy spectrum follows $k_ot^{-5/3}$ at fluid scales.

Steeper $k_ot^{-4}$ spectrum at sub-Larmor scales.

Development of a non-thermal power-law particle energy distribution.

Abstract

We present results from particle-in-cell simulations of driven turbulence in magnetized, collisionless, and relativistic pair plasma. We find that fluctuations are consistent with the classical $k_\perp^{-5/3}$ magnetic energy spectrum at fluid scales and a steeper $k_\perp^{-4}$ spectrum at sub-Larmor scales, where $k_\perp$ is the wavevector perpendicular to the mean field. We demonstrate the development of a non-thermal, power-law particle energy distribution, $f(E) \sim E^{-\alpha}$, with index $\alpha$ that decreases with increasing magnetization and increases with increasing system size (relative to the characteristic Larmor radius). Our simulations indicate that turbulence can be a viable source of energetic particles in high-energy astrophysical systems, such as pulsar wind nebulae, if scalings asymptotically become insensitive to the system size.