  The aim of the present study is to analyze the saturation regime of the
energetic-ion-driven resistive interchange mode (EIC) in the LHD plasma. A set
of non linear simulations are performed by the FAR3d code that uses a reduced
MHD model for the thermal plasma coupled with a gyrofluid model for the
energetic particles (EP) species. The hellically trapped EP component is
introduced through a modification of the averaged drift velocity operator to
include their precessional drift. The non linear simulation results show
similar 1/1 EIC saturation phases with respect to the experimental
observations, reproducing the enhancement of the n/m = 1/1 resistive
interchange modes (RIC) amplitude and width as the EP $\beta$ increases, the EP
beta threshold for the 1/1 EIC excitation, the further destabilization of the
1/1 EIC as the population of the helically trapped EP increases and the
triggering of burst events. The frequency of the 1/1 EIC calculated during the
burst event is 9.4 kHz and the 2/2 and 3/3 overtones are destabilized,
consistent with the frequency range and the complex mode structure measured in
the experiment. In addition, the simulation shows the inward propagation of the
1/1 EIC due to the non linear destabilization of the 3/4 and 2/3 EPMs, leading
to the partial overlapping between resonances during the burst event. Finally,
the analysis of the 1/1 EIC stabilization phase shows the excitation of the 1/1
RIC as soon as the flattening induced by the 1/1 EIC in the pressure profile
vanishes, leading to the retrieval of the pressure gradient at the plasma
periphery and the overcoming of the RIC stability limit.
