Force-free magnetic relaxation in driven plasmas

Area of Science:

• Plasma physics
• Magnetohydrodynamics
• Computational physics

Background:

• Taylor relaxation theory describes plasma states driven towards minimum energy.
• The Jensen-Chu theory predicts infinite energy and helicity barriers limiting accessible states in driven plasmas with boundary magnetic fields.
• These barriers restrict relaxed states to the system scale.

Purpose of the Study:

• To investigate the effect of nonlinearity on Taylor relaxation in partially relaxed force-free plasmas.
• To explore the accessibility of new plasma states beyond the Jensen-Chu barriers.
• To analyze the regularization of singularities by nonlinearity.

Main Methods:

• Theoretical analysis of the Jensen-Chu theory in the context of partially relaxed force-free plasmas (j=kB).
• Investigating the role of nonlinearity in regularizing singularities.
• Identifying new branches of accessible relaxed states.

Main Results:

• Nonlinearity in partially relaxed force-free plasmas regularizes the singularities predicted by the Jensen-Chu theory.
• Infinite energy and helicity barriers are overcome, allowing access to new relaxed states.
• New branches of relaxed states, including the flipped spheromak and high k states, become accessible.

Conclusions:

• Partial relaxation and nonlinearity are crucial for overcoming Jensen-Chu barriers in driven plasmas.
• This work expands the understanding of accessible states in plasma relaxation, beyond system-scale constraints.
• The findings have implications for magnetic confinement fusion and astrophysical plasmas.