  Current simulations of hot accretion flows around black holes assume either a
single-temperature gas or, at best, a two-temperature gas with thermal ions and
electrons. However, processes like magnetic reconnection and shocks can
accelerate electrons into a nonthermal distribution, which will not quickly
thermalise at the very low densities found in many systems. Such nonthermal
electrons have been invoked to explain the infrared and X-ray spectra and
strong variability of Sagittarius A* (Sgr A*), the black hole at the Galactic
Center. We present a method for self-consistent evolution of a nonthermal
electron population in the GRMHD code KORAL. The electron distribution is
tracked across Lorentz factor space and is evolved in space and time, in
parallel with thermal electrons, thermal ions, and radiation. In the present
study, for simplicity, energy injection into the nonthermal distribution is
taken as a fixed fraction of the local electron viscous heating rate. Numerical
results are presented for a model with a low mass accretion rate similar to
that of Sgr A*. We find that the presence of a nonthermal population of
electrons has negligible effect on the overall dynamics of the system. Due to
our simple uniform particle injection prescription, the radiative power in the
nonthermal simulation is enhanced at large radii. The energy distribution of
the nonthermal electrons shows a synchrotron cooling break, with the break
Lorentz factor varying with location and time, reflecting the complex interplay
between the local viscous heating rate, magnetic field strength, and fluid
velocity.
