Recent upgrades on BOUT++ framework

We report a few recent upgrades on BOUT++'s drift-reduced six-field turbulence model, in particular the flux-driven source option and the new Laplacian inversion solver which is able to capture $n=0$ mode evolution. With flux driven particle and energy sources from the core side, BOUT++ global simulations self-consistently evolve plasma backgrounds in transport time-scale runs. Moreover, in the previous simulations, due to numerical inaccuracy $n=0$ zonal mode is usually omitted when evaluating the electrostatic potential $\phi$ by inverting vorticity. Now a new Laplacian inversion solver that captures $n=0$ mode, first developed in Hermes-1 [1] -- a BOUT++ based five field model; and more recently in a four field shift circular model [2] has been extended and implemented in the six-field turbulence model, in both limited and diverted configurations. These improvements on BOUT++ is essential towards a fully self-consistent edge turbulence model capable of both transient (e.g., ELM, disruption) and transport time-scale simulations. [1] B. Dudson and J. Leddy, Plasma Phys. Control. Fusion \textbf{59} 054010 (2017) [2] H. Seto et.al, Phys. Plasma \textbf{26} 052507 (2019)