Fast magnetic reconnection in the plasmoid-dominated regime

Area of Science:

• Plasma Physics
• Astrophysics
• Fusion Energy

Background:

• Magnetic reconnection is a fundamental process in plasma physics, crucial for phenomena like solar flares and sawtooth crashes in fusion devices.
• Understanding the dynamics of resistive magnetic reconnection, particularly the role of plasmoids, is essential for predicting and controlling these events.

Purpose of the Study:

• To propose a conceptual model for resistive magnetic reconnection based on a stochastic plasmoid chain.
• To investigate the dependence of the global reconnection rate on plasma parameters and the flux distribution within plasmoids.
• To identify conditions leading to the formation of large plasmoids and their potential impact on reconnection dynamics and observable events.

Main Methods:

• Development of a conceptual model for resistive magnetic reconnection.
• Analytical investigation of the global reconnection rate and plasmoid flux distribution.
• Probabilistic analysis of the emergence of large plasmoids.
• Derivation of a criterion for the transition between resistive magnetohydrodynamic and collisionless regimes.

Main Results:

• The global magnetic reconnection rate is found to be independent of the Lundquist number.
• The distribution of fluxes within the plasmoids follows an inverse-square law.
• A finite probability exists for the formation of abnormally large plasmoids, capable of disrupting the plasmoid chain.
• A criterion for the transition from resistive magnetohydrodynamics (MHD) to the collisionless regime is established.

Conclusions:

• The proposed stochastic plasmoid chain model provides a framework for understanding resistive magnetic reconnection.
• The independence of the reconnection rate from the Lundquist number and the inverse-square flux distribution offer new insights into plasma dynamics.
• The potential for large plasmoid formation highlights a mechanism for abrupt events in astrophysical and laboratory plasmas.
• The derived criterion aids in distinguishing between different plasma regimes during reconnection.