Nonlinear Processes in Geophysics www.nonlin-processes-geophys.net 1023-5809 1607-7946 10 1/2 2003 10.5194/npg-10-37-2003 http://www.nonlin-processes-geophys.net/10/37/2003/ http://www.nonlin-processes-geophys.net/10/37/2003/npg-10-37-2003.html http://www.nonlin-processes-geophys.net/10/37/2003/npg-10-37-2003.pdf 37 44 0000-00-00 Phase-space holes due to electron and ion beams accelerated by a current-driven potential ramp M. V. Goldman D. L. Newman R. E. Ergun Center for Integrated Plasma Studies, University of Colorado at Boulder, USA Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, USA One-dimensional open-boundary simulations have been carried out in a current-carrying plasma seeded with a neutral density depression and with no initial electric field. These simulations show the development of a variety of nonlinear localized electric field structures: double layers (unipolar localized fields), fast electron phase-space holes (bipolar fields) moving in the direction of electrons accelerated by the double layer and trains of slow alternating electron and ion phase-space holes (wave-like fields) moving in the direction of ions accelerated by the double layer. The principal new result in this paper is to show by means of a linear stability analysis that the slow-moving trains of electron and ion holes are likely to be the result of saturation via trapping of a kinetic-Buneman instability driven by the interaction of accelerated ions with unaccelerated electrons.