Two-dimensional configuration of the magnetotail current sheet: THEMIS observations

Abstract

In this paper we investigate 2-D configuration of the magnetotail current sheet. We use measurements of magnetic field and plasma parameters by Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission in 2008-2009 to restore for the first time the current sheet configuration at three distances downtail (i.e., in the corresponding locations of THEMIS spacecraft: x <- 25RE, x ∼- 17RE, and x ∼- 10RE). The vertical velocity of current sheets (flapping motion) allows estimating the current sheet thickness L(x) and the current density j0(x)≈(c/4π)B0/L, where B0(x) is the amplitude of Bx field. We have shown that the current sheet configuration is more or less stable (spacecraft observe the same current sheet thickness and magnetic field amplitudes for successive crossings of the neutral plane) for time intervals around 1-3 h. The typical 2-D configuration of the magnetotail current sheet assumes the increase of L(x) and magnetic fields B0(x), Bz(x) toward the Earth, while the ratio Bz/B0 is almost constant along the magnetotail. Observed current sheets are very stretched with the typical scale of Bz(x) inhomogeneity LxLB0/2Bz. We compare obtained results with existing current sheet models.