Two-loop turbulent helical magnetohydrodynamics: Large-scale dynamo and energy spectrum

Area of Science:

• Plasma Physics
• Fluid Dynamics
• Theoretical Physics

Background:

• Helical magnetohydrodynamics (MHD) describes turbulent plasma behavior.
• Stationary turbulence in helical MHD presents challenges due to infrared instabilities.
• The magnetic response function in helical MHD exhibits an unstable 'masslike' term.

Purpose of the Study:

• To analyze incompressible helical MHD in fully developed stationary turbulence using a two-loop field-theoretic approach.
• To investigate mechanisms for stabilizing the system against the destabilizing 'masslike' term.
• To study the properties of the turbulent dynamo regime and emergent magnetic fields.

Main Methods:

• Two-loop field-theoretic analysis.
• Examination of loop diagrams in the magnetic response function.
• Analysis of the induction equation and symmetry breaking.

Main Results:

• Identified an infrared-unstable 'masslike' term perturbing Joule damping.
• Demonstrated two stabilization mechanisms: kinematic regime (external parameter) and turbulent dynamo regime (symmetry breaking).
• Showcased Goldstone-like corrections to Alfvén modes and anisotropic structures in the dynamo regime.
• Confirmed emergent magnetic fields steepen the magnetic energy spectrum slope to -11/3 + 2γ_{b★}.

Conclusions:

• Helical MHD turbulence requires stabilization mechanisms beyond the trivial ground state.
• Both kinematic and turbulent dynamo regimes offer pathways to a stable, large-scale magnetic field.
• The turbulent dynamo regime leads to complex emergent structures and modified energy spectra.