Abstract.The evolution of two counter-streaming electron beams is shown by means of 2-D kinetic simulations to lead to electron distributions and coherent localized bipolar plasma wave structures with features similar to those measured by the FAST satellite in the auroral ionosphere. Electrostatic whistler waves are generated at later times when the bipolar structures begin to lose coherence and break up in the dimension transverse to the geomagnetic field.

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The nonlinear stage of the two-stream instability in a 2D magnetized plasma produces electron phase-space tubes, the counterpart of phase-space holes in a 1D plasma. These tubes align primarily perpendicular to the magnetic field B 0 and have self-consistent bipolar electric fields parallel to B 0. Such bipolar electric fields have recently been observed in four different regions of the Earth's space plasma environment. Massively parallel 2D kinetic simulations show the dynamics of tube formation, evolution, and breakup, accompanied by the generation of electrostatic whistler waves. We focus on the breakup of the tubes and describe a new numerical study of tube stability.

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Abstract.Electron phase-space holes are regions of depleted electron density commonly generated during the nonlinear stage of the two-stream instability. Recently, bipolar electric field structures a signature of electron holes have been identified in the acceleration region of the auroral ionosphere. This paper compares the evolution of electron holes in 2-D and 3-D using massively-parallel PIC simulations. In 2-D, the holes decay after hundreds of plasma periods while emitting electrostatic whistler waves. In the 3-D simulations, electron holes also go unstable and generate whistlers but, due to physical processes not present in 2-D, energy flows out of the whistlers and into highly perpendicular lower hybrid modes. As a result of this difference, 3-D holes do not decay as far as 2-D holes. The differences between 2-D and 3-D evolution may have important implications for hole longevity and wave generation in the auroral ionosphere.