Bifurcated current sheet: model and Cluster observations

A model of the bifurcated current sheet

[1] Recent Geotail and Cluster observations revealed that thin current sheets in the near-Earth tail may have a bifurcated structure. In some cases the electrons are found to dominate the current. We present a generalization of the Harris current sheet equilibrium, which reproduces these features. The model ion distribution contains an additional element, viz. the quasi-adiabatic invariant of t...

A model of the bifurcated current sheet: 2. Flapping motions

[1] A generalization of the Harris [1962] model has recently been proposed to explain the multi-spacecraft Cluster observations of thin bifurcated current sheets. It utilizes features of the ion motion in thin sheets and assumes anisotropy of the ion species. We report the results of 2D PIC simulations based on this model. Simulations confirm its self-consistency. They also reveal the lower-hyb...

Current sheet flapping motion and structure observed by Cluster

[1] Fast vertical flapping oscillations of the plasma sheet have been observed by Cluster on September 26, 2001. The flapping motion had vertical speeds exceeding 100 km/s, an amplitude in excess of 1 RE and a quasiperiod of 3 min. The current sheet was mostly tilted in the Y-Z plane (with the tilt sometimes exceeding 45 ). The waves had the properties of a kink mode and propagated toward the d...

THEMIS two‐point measurements of the cross‐tail current density: A thick bifurcated current sheet in the near‐Earth plasma sheet

The basic properties of the near-Earth current sheet from 8 RE to 12 RE were determined based on Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations from 2007 to 2013. Ampere's law was used to estimate the current density when the locations of two spacecraft were suitable for the calculation. A total of 3838 current density observations were obtained to stu...

Quasi-adiabaticity in bifurcated current sheets