Evolution of currents and Ampere forces in current sheets are analyzed on the basis of magnetic measurements. Two new effects are observed in the current distributions at the later stage of the sheet evolution: first, a broadening of the current area at the side edges of the current sheet; second, a generation of reverse currents followed by their propagation from the edges to the center of the sheet. Super-thermal plasma flows moving across the width of the current sheet are observed by spectroscopic methods. The energies of plasma jets are consistent with the spatial structure and time dependences of the Ampere forces in the current sheets. The assumption is advanced that plasma acceleration may be more effective at the regions with lower plasma density, which are located at some distances from the sheet mid-plane. Generation of reverse currents provides an additional confirmation of transfer of energetic plasma jets toward the sheet edges.

We observed an unusual/anomalous asymmetry of the HeI 667.8 nm spectral line profiles emitted from the peripheral regions of a current sheet plasma, which is characterized by high electron density gradients. This asymmetry can be explained only by assuming that, in the plane perpendicular to the current in the sheet, there is a strong low-frequency oscillatory electric field, which considerably exceeds the ion electric microfield. Our calculations show that this field seems to correspond to either a circularly or nearly-circularly polarized wave in the current sheet plasma.

The profiles of the He II 3203 Å and He II 4686 Å spectral lines of helium ions have been detected and ana lyzed. Using these data, the processes of acceleration and heating of a plasma in current sheets that are formed in magnetic configurations with X type singular lines have been analyzed. The generation of plasma flows with energies of 400-1300 eV, which are much higher than the thermal energy of ions, has been revealed. The acceleration of the plasma induced by Ampere forces is likely spatially inhomogeneous, which should lead to shear plasma flows in a current sheet.

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The results of experimental research are presented on the fundamental possibility and conditions of the current sheet formation under high‐pressure He‐filling in the 2D magnetic fields with a null‐line. It was revealed that the formation of the current sheet and efficient plasma compression into the planar sheet could take place under high initial pressure, provided that the gradient of the magnetic field was large enough. The maximal electron density in the sheet peaked at ∼1017 cm—3 and was an order of magnitude higher than the initial electron density and the atomic density of the gas. Both the electron and ion temperatures were lower than 5 eV resulting in suppression of the electron thermal conductivity along the sheet surface. In these conditions the other loss channels played a dominant part, specifically the losses due to plasma radiation.