Experimental study of plasma compression into the sheet in three-dimensional magnetic fields with singular X lines

Abstract

The formation and evolution of the plasma sheets resulting from the plasma compression in diversified three-dimensional (3D) magnetic configurations with singular X lines are reported on. The research was focused on the correlation between the structure of a plasma sheet and the topology of the initial 3D magnetic configuration, especially on the impact of the guide field aligned with the X line. It has been demonstrated experimentally that plasma compression and formation of extended plasma sheets can take place in configurations with the X lines in the presence of a strong guide field. The electron density distributions in the plasma sheets were found to be rather sensitive to the magnetic field topology. The experiments revealed the effect of progressive decrease of the plasma compression ratio in response to increasing guide field. This effect has two basic manifestations: a decrease of the maximum plasma density and an enlargement of the sheet thickness. Based on the experimental data we advanced a concept that the deterioration of plasma compression into the sheet is due to enhancement of the guide field inside the sheet over its initial value, and due to excitation of additional currents in the plane perpendicular to the singular X line and to the original current in the sheet.