Self-Consistent Bootstrap Current Modeling with M3D-C1

Bootstrap current plays a crucial role in influencing the equilibrium of magnetic confinement devices. This current develops due to radial gradients in pressure and temperature, and is aligned to the magnetic field. In quasisymmetric (QS) stellarators and at the edge of tokamaks, bootstrap current often comprises the bulk of the electric current density and is essential for understanding the magnetohydrodynamic (MHD) equilibrium and stability of these configurations. This study expands the modeling capabilities of M3D-C1, an extended-MHD code, by implementing self-consistent physics models for bootstrap current. It employs two analytical frameworks, a generalized Sauter model [1] and a revised Sauter-like model [2] and uses the isomorphism described by Landreman [3] to apply these to quasisymmetric configurations. The implementation in M3D-C1 is benchmarked against neoclassical codes, including NEO, XGCa, and SFINCS. Notably, M3D-C1 is now uniquely equipped to perform self-consistent calculations of kinetic contributions to the plasma current for tokamaks and QS stellarators, establishing itself as a first-of-a-kind extended MHD code in this regard.



[1] Sauter, O., Angioni, C., & Lin-Liu, Y. R. Phys. of Plasmas, 6, 2834 (1999)



[2] Redl, A., et al.. Phys. Plasmas 28, 022502 (2021)



[3] Landreman, Buller, and Drevlak, Phys. Plasmas 29, 082501 (2022)