Hybrid and particle simulations of an interface expansion and of collisionless shock: A comparative and quantitative study

The release of a hot and dense drifted plasma into a background ambient mag netoplasma is analyzed with the help of one-dimensional hybrid and full par ticle electromagnetic simulations, in conditions approaching those commonly met in laboratory experiments. The overall study is mainly focused on the early times of the interaction between both plasmas and for a strictly perp endicular expansion in the magnetic field. Two successive regimes are evide nced: a "transitory" regime, where a characteristic interface builds up, fo llowed by a second regime, where a shock forms. Our purpose in this study i s to analyze in detail the differences inherent to each code, and to quanti fy their impact on the corresponding simulation results. Several difficulti es are identified throughout this comparison, since different assumptions a re used within each code; a method based both on the best time/space scale lengths fit and on a judicious choice of plasma and numerical parameters is proposed in order to overcome these difficulties. The present results and a similar comparative method may be easily extended when analyzing the dyna mics of the interface expansion building up in laboratory plasmas (during e xperiments of laser-target interactions), in space plasma (active experimen ts), and when applied to open questions related to collisionless shocks. (C ) 2001 American Institute of Physics.