Target scale dependence of laser-driven magnetized plasma dynamics in escargot geometries under fixed relativistic laser conditions

Abstract

Using particle-in-cell simulations, we investigate the effect of target scale on quasistatic axial magnetic-field generation in escargot microstructures under fixed laser conditions. By varying the base radius and gap length while preserving their ratio, we characterize the resulting field evolution using a bipolarity metric, peak field strengths, and magnetic fluxes. For gap lengths comparable to the beam waist, the generated field is predominantly positive. We attribute this to the combined effects of radial implosion, Lorentz force, and sustained whispering-gallery transport. As the target scale increases, the system transitions to a bipolar regime in which enhanced laser absorption leads to stronger return currents that dominate the magnetic-field topology. This scale-dependent behavior reflects a transition from laser-driven to transport-dominated dynamics, highlighting target geometry as a key control parameter for magnetic-field polarity in structured laser–plasma interactions.