Micro-macro coupling in plasma self-organization processes during island coalescence.

Area of Science:

• Plasma physics
• Astrophysics
• Space physics

Background:

• Collisionless magnetic reconnection is a fundamental process in plasma physics.
• Magnetic island coalescence is a key mechanism for magnetic self-organization in plasmas.
• Understanding the interplay between macroscopic and microscopic scales is crucial for plasma dynamics.

Purpose of the Study:

• To investigate the collisionless island coalescence process using particle-in-cell simulations.
• To determine the dependence of the macroscopic relaxation time on system scale and driving force.
• To elucidate the relationship between microscopic magnetic reconnection and macroscopic self-organization.

Main Methods:

• Particle-in-cell (PIC) simulations were employed to model the collisionless island coalescence.
• System scale and driving force strength were systematically varied.
• Macroscopic relaxation time was measured as the primary metric.

Main Results:

• Macroscopic relaxation time is critically dependent on the system scale.
• In small-scale systems, relaxation time is independent of the driving force, with reconnection enslaved by the macroscopic flux.
• In large-scale systems, relaxation time becomes dependent on the driving force, indicating a different regime of self-organization.

Conclusions:

• The scale of the system fundamentally governs the dynamics of collisionless island coalescence.
• Microscopic magnetic reconnection processes adapt to macroscopic conditions in small-scale systems.
• A transition in the self-organization mechanism occurs between small and large-scale systems, impacting energy dissipation and timescale.