Anomalous Heating and Plasmoid Formation in a Driven Magnetic Reconnection Experiment

Area of Science:

• Plasma Physics
• Astrophysics
• Magnetohydrodynamics

Background:

• Magnetic reconnection is a fundamental process in plasma physics, crucial for understanding phenomena in space and laboratory plasmas.
• Previous studies have often relied on simulations or observations of astrophysical plasmas, with laboratory experiments offering controlled environments for detailed investigation.

Purpose of the Study:

• To conduct a detailed study of magnetic reconnection in a quasi-two-dimensional pulsed-power laboratory experiment.
• To investigate the structure, dynamics, and energy partition during magnetic reconnection.
• To compare experimental observations with theoretical predictions, specifically semicollisional plasmoid theory.

Main Methods:

• Utilized a pulsed-power driven laboratory experiment to create a quasi-two-dimensional reconnection scenario.
• Employed temporally and spatially resolved optical diagnostics: interferometry, Faraday rotation imaging, and Thomson scattering.
• Measured plasma parameters including magnetic field strength, inflow velocities, current layer thickness, electron and ion temperatures.

Main Results:

• Observed the annihilation of oppositely directed magnetic fields (3 T) within a thin current layer (0.6 mm) driven by supersonic, sub-Alfvénic plasma flows (50 km/s).
• Measured significantly high electron (100 eV) and ion (600 eV) temperatures, exceeding classical dissipation predictions.
• Documented the repeated formation and ejection of plasmoids, aligning with semicollisional plasmoid theory.

Conclusions:

• The laboratory experiment successfully replicated key features of magnetic reconnection, including plasmoid dynamics.
• The observed high temperatures suggest non-classical dissipation mechanisms are at play during reconnection.
• Experimental results provide strong support for the predictions of semicollisional plasmoid theory in laboratory settings.