  The aim of the present study is to perform a theoretical analysis of
different strategies to stabilize energetic-ion-driven resistive interchange
mode (EIC) in LHD plasma. We use a reduced MHD 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 drift
frequency to include their precessional drift. The stabilization trends of the
1/1 EIC observed experimentally with respect to the thermal plasma density and
temperature are reproduced by the simulations, showing a reasonable agreement
with the data. The LHD operation scenarios with stable 1/1 EIC are identified,
leading to the stabilization of the 1/1 EIC if the thermal plasma density and
temperature are above a given threshold. The 1/1 EIC are also stabilized if the
rotational transform is modified in a way that the 1/1 rational surface is
located further away than 0.9 times the normalized radius, or the magnetic
shear in the plasma periphery is enhanced. Also, LHD discharges with large
magnetic fields show a higher EIC destabilization threshold with respect to the
thermal plasma density. If the perpendicular NBI deposition region is moved
further inward than 0.875 times the normalized radius the 1/1 EIC are also
stabilized. In addition, increasing the perpendicular NBI voltage such that the
EP energy is higher than 30 keV stabilizes the 1/1 EIC. Moreover, Deuterium
plasmas show a higher stability threshold for the 1/1 EIC than Hydrogen
plasmas. The experimental data shows a larger time interval between EIC events
as the power of the tangential NBI is increased providing that the
perpendicular NBI power is at least 13 MW. This implies a stabilizing effect of
the tangential NBI.
