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 magnetoplasma is analyzed with the help of one-dimensional hybrid and full particle 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 perpendicular expansion in the magnetic field. Two successive regimes are evidenced: a "transitory" regime, where a characteristic interface builds up, followed by a second regime, where a shock forms. Our purpose in this study is to analyze in detail the differences inherent to each code, and to quantify their impact on the corresponding simulation results. Several difficulties are identified throughout this comparison, since different assumptions are 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 dynamics of the interface expansion building up in laboratory plasmas (during experiments of laser-target interactions), in space plasma (active experiments), and when applied to open questions related to collisionless shocks. (C) 2001 American Institute of Physics.