Modeling ELM Pellet Pacing with M3D-C$^{1}$

M3D-C$^{1}$, a code for solving the linear or non-linear extended-MHD equations in toroidal geometry, is currently being used for modeling pellet ELM triggering in DIII-D ITER-like plasmas. Initial M3D-C$^{1}$ results run in linear mode show that the localized perturbation due to the pellet destabilizes peeling-ballooning modes. For these simulations the pellet was modeled as a 2D density ring perturbation and the total pressure was kept constant. Calculations of linear peeling-ballooning stability as a function of pellet size and deposition have shown for an initial number of particles = 4e17, only n$_{tor}$ = 20 is unstable. Increasing the number of particles to 1e19 leads to unstable edge modes at the pellet ablation location, suggesting that the 2-D pellet density ring underestimates the effects of the pellet. Linear simulations also suggest that the destabilization seems to be a resistive effect. Placing the density perturbation further inside the pedestal destabilizes n$_{tor}$ $>$ 10. Recent M3D-C$^{1}$ modeling efforts have focused on 3D, 2-fluid nonlinear simulations for ELM pellet pacing.