Nonthermal particle acceleration in simulations of relativistically hot plasma turbulence

In weakly collisional plasmas, particle interactions with turbulent fluctuations can result in plasma heating and nonthermal particle acceleration. Numerical simulations have shown that the particle energy probability density function (pdf) develops power-law tails at ultrarelativistic energies in both driven relativistically hot plasma turbulence [1] and decaying magnetically dominated plasma turbulence [2]. In [3], we presented a phenomenological model of nonthermal acceleration where particles are energized stochastically in magnetic traps and showed it to be in good agreement with 2.5D simulations of decaying magnetically dominated plasma turbulence. In this presentation, we extend our analysis to 3D simulations of both the driven and decaying cases. The theoretical spectral index of the particle energy pdf is compared to numerical observations and we discuss whether particle acceleration in driven relativistically hot turbulence that is only moderately magnetized should be attributed to particles interacting with turbulent fluctuations in the inertial range or the magnetic field on the outer scale.

[1] – Zhdankin, V., Uzdensky, D. A., Werner, G. R., Begelman, M. C. 2017, PhRvL, 118, 055103.

[2] – Comisso, L., Sironi, L. 2018, PhRvL, 121, 255101.

[3] – Vega, C., Boldyrev, S., Roytershteyn, V., & Medvedev, M. 2022, ApJL, 924, L19.