Formation of a quasi-one-dimensional current sheet in the laboratory experiment and in the Earth's magnetotail

Abstract

Two-dimensional current sheets (CSs) generated in the CS-3D laboratory device are considered. Results obtained in the laboratory experiment are compared with spacecraft observations of CSs in the Earth's magnetotail. The longitudinal and transverse CS structures, as well as CS evolution during the thinning process are studied. It is demonstrated that the CSs obtained in the laboratory experiments and those observed by spacecraft possess common properties: they have the same dimensionless spatial scales, similar distributions of the normal component of the magnetic field along the sheet, and similar ratios between the current density and the normal component of the magnetic field. The results of comparison allow one to guess some details of the structure and dynamics of the Earth's magnetotail CS. In particular, on the basis of the laboratory experiment, it is concluded that the formation of a quasi-one-dimensional CS in the magnetotail at distances of x ∼ ‑15R_E from the Earth (where R_E is the Earth' radius) is accompanied by the growth of the amplitude B₀ of the tangential component of the magnetic field and that the field B₀ in the quasi-stationary state increases tailward. The critical value of the current density is likely equal to $j_0 = eN_e \sqrt {2T_i m_i } $, where N_e is the electron density and $\sqrt {2T_i m_i } $ is the ion thermal velocity. The current density cannot substantially exceed this value. Moreover, the CS thickness cannot be substantially smaller then the ion Larmor radius or the ion inertial length.