Modeling laser-plasma interactions using extended magnetohydrodynamics

High-power lasers, while not yet reaching the Schwinger limit, are pivotal in various scientific domains, including laser fusion, particle acceleration, astrophysical phenomena, and even plasma optics for next-generation lasers. However, understanding laser-plasma interactions is often constrained by the high computational cost of numerical simulations required to resolve short temporal and spatial scales. Both non-collisional and collisional approaches are limited by the need for direct computation of electron motion. Non-collisional approaches typically use a kinetic approximation, while collisional approaches often model electrons and ions as independent fluids. This work shows how the generalized Ohm's law (GOL) captures laser absorption phenomena through macroscopic interactions of laser fields, electron flows, and ion dynamics, reproducing fundamental features like cut-off density, reflection, absorption and even ponderomotive force. This well-known force, arising from matter-light interactions, has especially significant implications for laser fusion instabilities. The ensuing ion density modulations can exacerbate fusion challenges like stimulated Brillouin scattering (SBS) and crossed-beam energy transfer (CBET), while also playing a role in astrophysical phenomena such as the dynamics of fast radio bursts. By incorporating electron effects on an ion timescale using a 1-fluid momentum/2-fluid energy extended magnetohydrodynamics (XMHD) model, this work demonstrates that ponderomotive effects are naturally present, enabling the study of problems too expensive for other numerical methods.