Tilted wire array explodes into quadrupolar density structures in first-of-its-kind study

Explosive astrophysical events, such as coronal mass ejections from the sun, happen because of magnetic reconnection, where oppositely directed magnetic field lines break apart and reconnect within a plasma. Often, these magnetic fields are not exactly opposite, and a component called a “guide field” does not reconnect and changes the rate of the process. Varnish et al. developed a first-of-its-kind platform that enables scientists to observe magnetic reconnection with guide fields across much larger length scales than previous studies.

The team’s hardware enables the study of pulsed-power driven magnetic reconnection with an embedded, variable-strength guide field — a phenomenon that has not been experimentally observed before. Verifying theoretical predictions, the team observed reconnection layers with a quadrupolar density structure.

“Understanding the global structure of the reconnection layer in the guide field regime is important for developing interpretations of spacecraft data, which cannot directly measure the global properties of the layer but instead observe slices of the reconnection layer as they pass through,” author Thomas Varnish said.

The team used dime-sized exploding wire arrays made of mechanical pencil refills to generate plasma for their experiments. They passed an intense current pulse through the wires using a pulsed-power machine, ohmically heating them and rapidly turning them from a solid into a plasma. Placing two such arrays beside each other resulted in magnetic reconnection occurring in the region between them. Two laser interferometers oriented along orthogonal lines of sight enabled the team to discern the reconnection layer’s 3D structure.

The team’s future work includes modifying their hardware to produce reconnection layers with less complex geometries and experimentally verifying the modified properties of the layer predicted by theory.

Source: “Quadrupolar density structures in driven magnetic reconnection experiments with a guide field,” by T. W. O. Varnish, J. Chen, S. Chowdhry, R. Datta, G. V. Dowhan, L. S. Horan IV, N. M. Jordan, E. R. Neill, A. P. Shah, R. Shapovalov, B. J. Sporer, R. D. McBride, and J. D. Hare, Physics of Plasmas (2025). The article can be accessed at https://doi.org/10.1063/5.0251581 .