Using three-dimensional (3D) magnetohydrodynamic simulations, we study how a pit on a metal surface evolves when driven by intense electrical current density $\mathbf{j}$. Redistribution of $\mathbf{j}$ around the pit initiates a feedback loop: $\mathbf{j}$ both reacts to and alters the electrical conductivity $\sigma$, through Joule heating and hydrodynamic expansion, so that $\mathbf{j}$ and $\sigma$ are constantly in flux. Thus, the pit transforms into larger striation and filament structures predicted by the electrothermal instability theory. Both structures are important in applications of current-driven metal: The striation constitutes a density perturbation that can seed the magneto-Rayleigh-Taylor instability, while the filament provides a more rapid path to plasma formation, through 3D j redistribution. Simulations predict distinctive self-emission patterns, thus allowing for experimental observation and comparison.

• Received 24 February 2023
• Accepted 30 May 2023

DOI:https://doi.org/10.1103/PhysRevE.107.065209