Paper detail

Controlling the level of the ideal invariant fluxes for MHD turbulence using TURBO spectral solver

The ideal invariants present in the formalism of magnetohydrodynamics (MHD), i.e. global quantities that are conserved in the absence of sources and dissipative effects, play an important role in various theoretical and numerical studies of MHD turbulence. The fluxes of these ideal invariants represent separate channels that transfer the information across different scales in a turbulent system. Once a statistically stationary state of turbulence is reached, the amount of any ideal invariant quantity introduced in the system by a forcing mechanism equals the amount of the same quantity removed by the dissipative effects from the system. For highly developed turbulence, these two mechanisms act predominantly at different scales that are largely separated. Since the ideal invariant quantities cascade between scales, a constant flux is generated with great implication on the state of the system. Numerically, controlling the ideal invariant fluxes levels for a turbulent MHD system is important for the analysis of fundamental MHD turbulence properties. We propose a forcing mechanism that controls the three ideal invariants of MHD turbulence: the total energy, the cross-helicity and the magnetic helicity. This forcing is implemented in the freely available TURBO solver, that is also briefly presented.