  Turbulence in tokamaks generates radially sheared zonal flows. Their
oscillatory counterparts, geodesic acoustic modes (GAMs), appear due to the
action of the magnetic field curvature. The GAMs can be driven unstable by an
anisotropic energetic particle (EP) population leading to the formation of
global radial structures, called EGAMs. The EGAMs can redistribute EP energy to
the bulk plasma through collisionless wave-particle interaction. In such a way,
the EGAMs might contribute to the plasma heating. Thus, investigation of EGAM
properties, especially in the velocity space, is necessary for precise
understanding of the transport phenomena in tokamak plasmas.
  In this work, the nonlinear dynamics of EGAMs without considering the mode
interaction with the turbulence is investigated with the help of a
Mode-Particle-Resonance (MPR) diagnostic implemented in the global gyrokinetic
particle-in-cell code ORB5. An ASDEX Upgrade discharge is chosen as a reference
case for this investigation due to its rich EP nonlinear dynamics. An
experimentally relevant magnetic field configuration, thermal species profiles
and an EP density profile are taken for EGAM chirping modelling and its
comparison with available empirical data. The same magnetic configuration is
used to explore energy transfer by the mode from the energetic particles to the
thermal plasma including kinetic electron effects. For a given EGAM level the
plasma heating by the mode can be significantly enhanced by varying the EP
parameters. Electron dynamics decreases the EGAM saturation amplitude and
consequently reduces the plasma heating, even though the mode transfers its
energy to thermal ions much more than to electrons.
