A warm fluid model of intense laser-plasma interactions

Summary form only given. Much of the physics relevant to understanding the interaction of intense laser pulses with underdense plasmas is contained in the Vlasov-Maxwell equations. In limited, specialized cases, analytical progress can be made towards solving the Vlasov equation, but in full generality, the Vlasov-Maxwell system is considered to be intractable to analytic solution. Fluid models (both warm and cold) represent a significant simplification over full kinetic treatments of plasma dynamics while retaining enough physics to be qualitatively and quantitatively useful approximation. For the configurations of interest to us (namely, those associated with advanced accelerator concepts), the bulk motion of the plasma is relativistic and the fractional spread in momentum is typically very small. This regime is in contrast to the usual regime of relativistic thermodynamics where the momentum spread is assumed to very large (i.e., high temperature). Following up on our previous work on modeling intense laser-plasma interactions with cold fluids, we are exploring warm fluid models. These models represent the next level in a hierarchy of complexity beyond the cold fluid approximation. With only a modest increase in computation effort, warm fluids incorporate effects that are relevant to a variety of technologically interesting cases. We present a derivation of the relativistic warm fluid from a kinetic (i.e. Vlasov) perspective and expand on the connection with the usual relativistic thermodynamic approach. We will provide examples in both one and two dimensions and discuss experimental parameters where these effects are believed to be important.