Particle accceleration in relativistically hot plasmas

In a weakly collisional plasma, particle interactions with turbulent fluctuations may lead to plasma heating. In recent numerical kinetic studies of relativistically hot plasmas, a power law tail was observed in the particle energy distribution function at ultra-relativistic energies (e.g., [1], [2]). In our previous work we proposed a phenomenological model of particle energization in which particles are magnetically trapped and accelerated in turbulent structures until they escape due to pitch angle scattering [3]. A formula for the power law observed in the particle energy pdf was derived and compared to the results of VPIC simulations. On this presentation we discuss this model and check it against a broader range of strengths of the background magnetic field relative to the magnetic fluctuations.

[1] - Comisso, L., Sironi, L. 2019, ApJ, 886, 122.

[2] - Zhdankin, V., Uzdensky, D. A., Werner, G. R., Begelman, M. C. 2019, PhRvL, 122, 055101.

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