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Alfven Eigenmodes (AE) can be destabilized by energetic particles in neutralbeam injection (NBI) heated plasmas through inverse Landau damping andcouplings with gap modes in the shear Alfven continua. We describe the linearevolution of the poloidal flux and the toroidal component of the vorticity in afull 3D system using the reduced MHD equations, density and parallel velocitymoments for the energetic particles as well as the geodesic acoustic wavedynamics. A closure relation adds the Landau damping and resonantdestabilization effects in the model. We apply the model to study the Alfvenmodes stability in TJ-II, performing a parametric analysis in a range ofrealistic values of energetic particle $\beta$ (beta_f), ratios ofthermal/Alfven velocities (Vth/VA0), energetic particle density profiles andtoroidal modes (n) including toroidal and helical couplings. The study predictsa large helical coupling between different toroidal modes and thedestabilization of helical Alfven Eigenmodes (HAE) with frequencies similar tothe AE activity measured in TJ-II, between 50 - 400 kHz. The analysis has alsorevealed the destabilization of GAE (Global Alfven Eigenmodes), TAE (ToroidalAlfven Eigenmodes) and EPM (Energetic Particle Modes). For the modes consideredhere, optimized TJ-II operations require a iota profile in the range of [0.845,0.979] to stabilize AEs in the inner and middle plasma. AEs in the plasmaperiphery cannot be fully stabilized, although for a configuration with iota =[0.945, 1.079], only n=7,11,15 AE are unstable with a growth rate 4 timessmaller compared to the standard iota = [1.54,1.68] case and a frequency of 100kHz. We reproduce the frequency sweeping evolution of the AE frequency observedin TJ-II as the iota profile is varied. The AE frequency sweeping is caused byconsecutive changes of the instability dominant modes between different helicalfamilies.

Analysis of Alfven Eigenmodes destabilization by energetic particles in TJ-II using a Landau-closure model