Externally driven bifurcation of current sheet: A particle-in-cell simulation

A current sheet is a confined layer of electric current in the presence of a strong magnetic gradient, which exists ubiquitously in space and the universe. Magnetic energy is stored in current sheets and then potentially released through processes such as magnetic reconnection. Spacecraft observations show that some current sheets in Earth's magnetotail are bifurcated with a double-peak current density profile. The cause of this bifurcation, however, is still unclear. Here, using a particle-in-cell simulation, we show the bifurcation is formed when the current sheet is thinned by an external driver. In this process, an electron pressure anisotropy (p(e perpendicular to) > p(e parallel to)) is formed at the center of the current sheet, which decreases the current density at the center, leading to the bifurcated profile of the current density.