Computer Simulations Of Electron Hole

Previous study predict that muti-dimensional electron phase-space holes can be destroyed by the transverse instability and lower hybrid waves in different plasma parameters. In this paper, we perform two-dimensional(2D) Particle-in-cell(PIC) simulations to study the evolution of holes at different plasma parameters; we find that the evolution can be determined by the combine actions between the transverse instability and the stabilization by the background magnetic field when the ions dynamics are neglected; and the evolution of the electron holes can be strongly affected by the ions dynamics. With the increase of the ions dynamics, electron holes evolve more rapid and destroyed in a shorter time. When we consider the ions effects, we find that the electron holes in the condition of the real mass ratio(mi/me=1836) are destroyed by the transverse instability in the weakly magnetized plasma, while the electron holes in the condition of the real mass ratio(mi/me=1836) can be destroyed by the qwasi-perpendicular lower hybrid waves in the strongly magnetized plasma.In this paper, two-dimensional particle-in-cell simulations are performed to investigate magnetic structures associated with electron holes in different plasma parameters. In this simulations, the background magnetic field (B0=B0ex) is along the x direction. The combined actions leading to the generation of the electric field Ey are transverse instability and stabilization by the background magnetic. Then electrons drift in the z direction and produce the current, which leads to the fluctuating magnetic field in the direction of x and y. While the electron holes move along the x direction and with the combined actions between the drifting velocity and the electric field Ey, the fluctuating magnetic field along the z direction is generated. In the weakly magnetized plasma (Ωe<<ωpe), transverse instability is dominated and the magnetic structures disappear with electron holes rapidly.An electron phase-space hole (electron hole) is considered to be unstable to the transverse instability. In this paper, two-dimensional (2D) electrostatic particle-in cell(PIC) simulations are used to explore the dissipation of a one-dimensional (ID) electron hole in a weakly magnetized plasma and its consequence on electron heating, which consists of two stages. In the first stage, the electron hole is still kept as a quasi-1D structure, however, with the excitation of the transverse instability and the generation of the perpendicular electric field, the electrons are scattered and then heated along the perpendicular direction in the electron hole. In the second stage, the quasi-ID electron hole is broken into several2D electron holes. The temperature of the electrons outside of these2D electron holes also increase, and at last the velocity distribution of the electrons become almost isotropic in the whole simulation domain. Our results provide a new dissipation mechanism of an electron hole.In this paper, two-dimensional particle-in-cell simulations are performed to investigate the characteristics of these electron holes generated in the separatrix region of antiparallel magnetic reconnection. The electron holes with bipolar structures of the parallel electric field are formed in the border between the electron inflow channel (where electrons move toward the X line) and outflow channel (where electrons flow away from the X line), where the electrons satisfy the bump-on-tail distribution. Quasi-monochromatic electrostatic waves, which propagate with a speed near the bulk velocity of the fast electron beam, are first excited by the electron bump-on-tail instability. These waves then coalesce with each other, and at last electron holes are formed in the separatrix region which then propagate away from the X line along the magnetic field lines.Previous particle-in-cell simulations have shown that electron phase-space holes (electron holes), where the associated parallel electric field has a bipolar structure, exist near the four separatrices in anti-parallel magnetic reconnection. In this paper, by performing two-dimensional (2-D) particle-in-cell (PIC) simulations, we investigate magnetic reconnection in an asymmetric current sheet, with emphasis on the parallel electric field near the separatrices. Compared with magnetic reconnection in a symmetric current sheet, we found that the parallel electric field with a bipolar structure only exists around the separatrices in the upper region with a lower density (upper separatrices). Such a bipolar structure of the parallel electric field is considered to be associated with electron holes resulting from the nonlinear evolution of the electron beam instability excited by the high-speed electron flow formed after their acceleration around the X line. The disappearance of the parallel electric field around the separatrices in the lower region with a higher density (lower separatrices) may be due to the transverse instability, which is unstable in a weak magnetized plasma.