Large-scale magnetic fields at high Reynolds numbers in magnetohydrodynamic simulations

The 11-year solarmagnetic cycle shows a high degree of coherence in spite of the turbulent nature of the solar convection zone. It has been found in recent high-resolutionmagnetohydrodynamics simulations that the maintenance of a large-scale coherent magnetic field is difficult with small viscosity and magnetic diffusivity (≲10¹² square centimenters per second).We reproduced previous findings that indicate a reduction of the energy in the large-scalemagnetic field for lower diffusivities and demonstrate the recovery of the global-scalemagnetic field using unprecedentedly high resolution. We found an efficient small-scale dynamo that suppresses small-scale flows, which mimics the properties of large diffusivity. As a result, the global-scale magnetic field is maintained even in the regime of small diffusivities - that is, large Reynolds numbers.