Properties of current sheet thinning at x ≈-10 to-12RE

We report on Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations of current sheet thinning in Earth's magnetotail at around x =- 10 to -12 Earth radii. The THEMIS spacecraft configuration in October-December 2015 allows us to construct both gradients that contribute to the cross-tail current density jy=0-1(Bx/z-Bz/x) (GSM coordinates). For 17 events when the spacecraft observed a gradual B-z decrease and j(y) increase, we find the following average scaling relations: for the current density jy approximate to Bz-7/4, for the lobe magnetic field BL approximate to Bz-1/4, and for the plasma density ni approximate to Bz-3/4. We show that the temperature of ions and electrons decreases and the plasma pressure gradient p/x rapidly increases during current sheet thinning. The scale Lx=(lnp/x)-1 decreases a few thousand kilometers. We also consider current carriers in thinning current sheets: both ion and electron current-dominated current sheets, preferentially located near dusk and midnight, respectively, are found.