Plasma pressure response to non-inductive current drive in axisymmetric visco-resistive MHD steady-states

TL;DR

This paper models axisymmetric tokamak plasma steady-states using visco-resistive MHD, highlighting the importance of non-inductive current drives for realistic pressure profiles and revealing complex magnetic structures when current reversals occur.

Contribution

It introduces a new formulation for pressure profiles in visco-resistive MHD models and demonstrates the impact of non-inductive current drives on plasma equilibrium.

Findings

Non-inductive current drives improve pressure profile realism.

Current reversals lead to non-nested flux surfaces.

Moderate effects on velocity profiles observed.

Abstract

We investigate self-consistent, steady-state axisymmetric solutions of incompressible tokamak plasma using a visco-resistive magnetohydrodynamic model. A key contribution of this work is the formulation of Poisson's equation that governs the pressure profile. Our analysis reveals that the current modeling fails to produce realistic pressure levels. To overcome this limitation, we introduce additional non-inductive current drives, akin to those generated by neutral beam injection or radio frequency heating, modeled as modifications to the toroidal current. Numerical simulations validate our enhanced model, showing significant improvements in pressure profile characteristics. In the cases examined, the effect of these current drives on the velocity profiles is moderate, except when the non-inductive current drives induce reversals in the total toroidal current density, leading to non-nested flux surfaces with internal separatrices.