Phase-space electron holes along magnetic field lines

Recent observations from satellites crossing active magnetic field lines ha ve revealed solitary potential structures that move at speeds substantially greater than the ion thermal velocity. The structures appear as positive p otential pulses rapidly drifting along the magnetic field. We interpret the m as BGK electron holes supported by a population of trapped and passing el ectrons. Using Laplace transform techniques, we analyse the behavior of one phase-space electron hole. The resulting potential shapes and electron dis tribution functions are self-consistent and compatible with the field and p article data associated with the observed pulses. In particular, the spatia l width increases with increasing amplitude. The stability of the analytic solution is tested by means of a two-dimensional particle-in-cell simulatio n code with open boundaries. We also use our code to briefly investigate th e influence of the ions. The nonlinear structure appears to be remarkably r esilient.