Study of transition between even and odd toroidal Alfv\'en eigenmodes on EAST using NIMROD*

Linear simulations of toriodal Alfv\'en eigenmodes (TAEs) driven by energetic particles (EPs) on EAST are performed using the hybrid-kinetic MHD model implemented in the NIMROD code. The "slowing down" distribution is adopted for modeling the equilibrium distribution of the energetic ions from the deuterium neutral beam injection on EAST. The frequency, the dominant poloidal mode number, the radial location, and the detailed 2D mode structure of the TAE/RSAE/EPM modes are consistent between the eigenvalue analysis and the NIMROD calculation. As the EP $\beta$ fraction increases, a transition between even and odd TAEs occurs, along with that between the ballooning and anti-ballooning mode structures. When the EP $\beta$ fraction is close to the transition threshold, both types of TAEs coexist.