Kinetic Turbulence in Relativistic Plasma: From Thermal Bath to Nonthermal Continuum.

We present results from particle-in-cell simulations of driven turbulence in magnetized, collisionless, and relativistic pair plasmas. We find that the fluctuations are consistent with the classical k_{⊥}^{-5/3} magnetic energy spectrum at fluid scales and a steeper k_{⊥}^{-4} spectrum at sub-Larmor scales, where k_{⊥} is the wave vector perpendicular to the mean field. We demonstrate the development of a nonthermal, power-law particle energy distribution f(E)∼E^{-α}, with an index α that decreases with increasing magnetization and increases with an 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.