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Abstract: The excitation of magnetosonic waves in the meridian plane of a rescaled dipole magnetic field is investigated, for the first time, using a general curvilinear particle‐in‐cell simulation. Our simulation demonstrates that the magnetosonic waves are excited near the equatorial plane by tenuous ring distribution protons. The waves propagate nearly perpendicularly to the background magnetic field along both radially inward and outward directions. Different speeds of inward and outward propagation result in the asymmetrical distribution about the source region. The waves are accompanied by energization of both cool protons and electrons near the wave source region. The cool protons are heated perpendicularly, while the cool electrons can be heated in the parallel direction and also experience enhanced perpendicular drift at the presence of intense wave power. The implications of simulation results to the observations of magnetosonic waves and related particle heating in the inner magnetosphere are also discussed. [ABSTRACT FROM AUTHOR]

It is well known that the parallel cuts of the parallel and perpendicular electric field in electron phase-space holes (electron holes) have bipolar and unipolar structures, respectively. Recently, electron holes in the Earth's plasma sheet have been observed by THEMIS satellites to have detectable fluctuating magnetic field with regular structures. Du et al. () investigated the evolution of a one-dimensional (1D) electron hole with two-dimensional (2D) electromagnetic particle-in-cell (PIC) simulations in weakly magnetized plasma (Ω< ω, where Ω and ω are the electron gyrofrequency and electron plasma frequency, respectively), which initially exists in the simulation domain. The electron hole is unstable to the transverse instability and broken into several 2D electron holes. They successfully explained the observations by THEMIS satellites based on the generated magnetic structures associated with these 2D electron holes. In this paper, 2D electromagnetic particle-in-cell (PIC) simulations are performed in the x- y plane to investigate the nonlinear evolution of the electron two-stream instability in weakly magnetized plasma, where the background magnetic field $(\mathbf{B}_{0} =B_{0}\vec{\mathbf{e}} _{x})$ is along the x direction. Several 2D electron holes are formed during the nonlinear evolution, where the parallel cuts of E and E have bipolar and unipolar structures, respectively. Consistent with the results of Du et al. (), we found that the current along the z direction is generated by the electric field drift motion of the trapped electrons in the electron holes due to the existence of E, which produces the fluctuating magnetic field δB and δB in the electron holes. The parallel cuts of δB and δB in the electron holes have unipolar and bipolar structures, respectively. [ABSTRACT FROM AUTHOR]

Electron phase space holes (electron holes) are found to be unstable to the transverse instability. Two-dimensional (2D) electromagnetic particle-in-cell simulations are performed to investigate the structures of the fluctuating magnetic field associated with electron holes. The combined actions between the transverse instability and the stabilization by the background magnetic field (B0=B0evector x) lead a one-dimensional electron hole into several 2D electron holes which are isolated in both the x and y directions. The electrons trapped in these 2D electron holes suffer the electric field drift vE=E×B0/B02 due to the existence of the perpendicular electric field Ey, which generates the current along the z direction. Then, the unipolar and bipolar structures are formed for the parallel cut of the fluctuating magnetic field along the x and y directions, respectively. At the same time, these 2D electron holes move along the x direction, and the unipolar structures are formed for the parallel cut of the fluctuating magnetic field along the z direction. [ABSTRACT FROM AUTHOR]

Two-dimensional particle-in-cell simulations are performed to investigate the formation of electron density depletions in collisionless magnetic reconnection. In anti-parallel reconnection, the quadrupole structures of the out-of-plane magnetic field are formed, and four symmetric electron density depletion layers can be found along the separatrices due to the effects of magetic mirror. With the increase of the initial guide field, the symmetry of both the out-of-plane magnetic field and electron density depletion layers is distorted. When the initial guide field is sufficiently large, the electron density depletion layers along the lower left and upper right separatrices disappear. The parallel electric field in guide field reconnection is found to play an important role in forming such structures of the electron density depletion layers. The structures of the out-of-plane magnetic field By and electron depletion layers in anti-parallel and guide field reconnection are found to be related to electron flow or in-plane currents in the separatrix regions. In anti-parallel reconnection, electrons flow towards the X line along the separatrices, and are directed away from the X line along the magnetic field lines just inside the separatrices. In guide field reconnection, electrons can only flow towards the X line along the upper left and lower right separatrices due to the existence of the parallel electric field in these regions. [ABSTRACT FROM AUTHOR]

In collisionless reconnection, the magnetic field near the separatrix is stronger than that around the X-line, so an electron-beam can be formed and flows toward the X-line, which leads to a decrease of the electron density near the separatrix. Having been accelerated around the X-line, the electrons flow out along the magnetic field lines in the inner side of the separatrix. A quadruple structure of the Hall magnetic field By is formed by such a current system. A 2D particle-in-cell (PIC) simulation code is used in this paper to study the collisionless magnetic reconnection without an initial guide field. The current system described above is proved by the simulations. Furthermore, the position of the peak of the Hall magnetic field By is found to be between the separatrix and the center of the current sheet, which is verified by Cluster observations. [ABSTRACT FROM AUTHOR]