Collective Effects Triggered by Individual Effects in One‐Dimensional Plasmas

Abstract

The relationship between individual and collective effects in a two‐component plasma is investigated in the case of an unstable equilibrium given by a cold two‐stream distribution. The full dynamics of this system is solved using an exact N‐body code. As the graininess parameter is large, such a cold plasma should be dominated by individual effects. Indeed, during an initial phase much longer than the plasma period, ions and electrons simply oscillate around each other forming neutral “molecules.” Subsequently, however, the system switches to a regime where collective effects are important: the two‐stream configuration becomes unstable and phase space structures appear. On a longer time scale, the streams are destroyed and the system evolves towards thermal equilibrium. The present results show that collective effects can emerge even in a plasma dominated by individual interactions, provided that the initial distribution is unstable.

Keywords:

• Strongly correlated plasmas
• two‐stream instability
• numerical simulations

Acknowledgment

The authors thank M.R. Feix for several useful suggestions.