Formation of self‐organized shear structures in thin current sheets

Abstract

Self-consistent kinetic (particle-in-cell) model of magnetotail thin current sheet (TCS) is used to understand the formation of self-consistent sheared magnetic structures. It is shown that shear configurations appear in TCS as a result of self-consistent evolution of some initial magnetic perturbation at the current sheet center. Two general shapes of shear TCS components are found as a function of the transverse coordinate: symmetric and antisymmetric. We show that TCS formation goes together with the emergence of field-aligned currents in the center of the current sheet, as a result of north-south asymmetry of quasi-adiabatic ion motions. Ion drift currents can also contribute to the magnetic shear evolution, but their role is much less significant, their contribution depending upon the normal component B z and the amplitude of the initial perturbation in TCS. Parametric maps illustrating different types of TCS equilibria are presented that show a higher probability of formation of symmetric shear TCS configuration at lower values of the normal magnetic component.

Equilibrium Configurations of Super‐Thin Current Sheets in Space Plasma: Characteristic Scaling of Multilayer Structures

“…The shear component of the magnetic field $${B}_{y}$$ is often observed and can penetrate into the magnetotail from the interplanetary space (Sergeev, 1987) or can be formed self‐consistently (Grigorenko et al., 2015; Malova et al., 2015, and references therein). It can influence the dynamics of current carriers near the neutral plane (Büchner & Zelenyi, 1991; Kaufmann et al., 1994; Malova et al., 2012; Shen, Liu, et al., 2008; Shen, Rong, et al., 2008; Zhu & Parks, 1993) and modify the TCS structure (Cowley, 1981; Hilmer & Voigt, 1987; Malova et al., 2012, 2015).…”

“…A shear component of the magnetic field is a very important one, because it could really change the TCS location as well as its shape and thickness in comparison with the shearless case (e.g., Petrukovich et al., 2011, Shen, Liu, et al., 2008; Shen, Rong, et al., 2008; Malova et al., 2012). The shear component of the magnetic field $${B}_{y}$$ is often observed and can penetrate into the magnetotail from the interplanetary space (Sergeev, 1987) or can be formed self‐consistently (Grigorenko et al., 2015; Malova et al., 2015, and references therein). It can influence the dynamics of current carriers near the neutral plane (Büchner & Zelenyi, 1991; Kaufmann et al., 1994; Malova et al., 2012; Shen, Liu, et al., 2008; Shen, Rong, et al., 2008; Zhu & Parks, 1993) and modify the TCS structure (Cowley, 1981; Hilmer & Voigt, 1987; Malova et al., 2012, 2015).…”

Current sheets in planetary magnetospheres

“…Electron drift currents [49], the presence of oxygen heavy ions [77] and the accumulation of quasi-trapped plasma in TCSs [74] represent realistic factors that influence the formation of complex multiscale profiles with several embedded CSs with different thicknesses in a different planetary magnetospheres [22,46,47]. Factors such as the shear magnetic component or the natural fluctuations of plasma sources can also lead to the formation of asymmetric TCS current density profiles [11,50,52,80]. All these TCS configurations can have different structures and conditions of stability because they are mostly determined not by macroscopic characteristics of plasma flows but by the peculiar kinetic effects operating within the TCS.…”