Mechanisms for laser-plasma interaction and their macroscopic effects within the extended MHD framework*

Modeling lasers interacting with z-pinch plasma is made particularly computationally intense due to the range of scales required.  Z-pinch simulations typically require μm/ns spatiotemporal scales, while laser-plasma interaction (LPI) can require sub-nm and pico/femtosecond resolutions.  This problem is usually handled by hybrid codes,  but for short laser interactions the fluid approximation may give a relatively accurate picture of flow dynamics on macroscopic scales due to strictly enforcing mass, momentum and energy conservation.  A question that deserves attention is exactly what mechanism within the XMHD framework (such as PERSEUS) performs the coupling between electromagnetic wave and plasma.  For hybrid codes, the laser energy can be deposited by ray-tracing and ponderomotive force.  However, for XMHD that includes electron inertia, although the full set of Maxwell's equations are solved, the interaction occurs within Generalized Ohm's Law.  The fluid approach replicates several features usually associated with PIC such as a cut-off density, hole-boring, and density fringes.  We will explore these to understand how they are related to the analogous theoretical effects.