  Direct numerical simulations of 3D compressible MHD turbulence were performed
in order to study the relation between waves modes and coherent structures and
the consequent energization of test particles. Moreover, the question of which
is the main mechanism of this particle energization is rigorously discussed. In
particular, using the same initial conditions, we analyzed the non-linear and
linear evolution of a turbulent state along with the case of randomized phases.
Then, the behavior of the linear and non-linear simulations were compared
through the study of time evolution of particle kinetic energy and preferential
concentration. Also, spatio temporal spectra were used to identify the presence
of wave modes and quantify the fraction of energy around the MHD modes in
linear and non-linear simulations. Finally, the variation of the correlation
time of the external forcing is studied in detail along with the effect on the
particle energization (and clustering) and the presence of wave modes. More
specifically, particle energization tends to decrease when the fraction of
linear energy increase, supporting the idea that energization by structures is
the dominant mechanism for particle energization instead of resonating with
wave modes as suggested by Fermi energization theory.
