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This study investigates magnetic reconnection — a fundamental plasma physics process — using pulsed-power-driven experiments where two exploding wire arrays generate colliding plasma flows carrying anti-parallel magnetic fields of approximately 1.2 T. The researchers found that without an external field, or with a weak one (0.5 T), a dense reconnection layer forms as expected from prior work; however, applying a strong external field (2 T) parallel to the reconnecting electric field suppresses this layer, producing instead a void between the plasma flows. The team hypothesizes that the external field becomes frozen into the plasma, generating a back-pressure that decelerates the flows and delays current sheet formation — a conclusion supported by three-dimensional magnetohydrodynamic (MHD) simulations.
Why it matters
Understanding how external magnetic fields influence reconnection dynamics is relevant to space and astrophysical plasma environments (such as the Earth's magnetosphere and solar flares) as well as to controlled fusion research, where managing magnetic reconnection events is critical for plasma stability.
arXiv:2605.15427v1 Announce Type: new
Abstract: We present results from pulsed-power-driven magnetic reconnection experiments, in which we drove two exploding wire arrays in parallel to produce colliding plasma flows with anti-parallel magnetic fields of 1.2$pm$0.2 T. The experimental volume was surrounded by a Helmholtz coil pair capable of externally applying a field of up to 2 T, parallel to the reconnecting electric field. We diagnosed these experiments using laser interferometric imaging in the direction of the anti-parallel magnetic fields, gated extreme ultraviolet pinhole imaging, and in situ inductive probes. For zero and weak (0.5 T) external fields, we reproduce previous observations in which a dense reconnection layer forms between the two wire arrays. However, when we apply a strong external field (2 T), we observe a void between the arrays rather than a dense layer, and we hypothesise that the external field is frozen out of the plasma and provides a back-pressure which decelerates the flows. Our experimental results are compared with three-dimensional magnetohydrodynamic simulations of the experiment, which qualitatively support this hypothesis. These simulations allow us to study the pressure balance and dynamics of the current sheet aspect ratio, demonstrating the delayed formation of the reconnection layer due to the external field.