Experimental study of current sheet evolution in magnetic configurations with null-points and X-lines

A review is presented on experimental research of current sheet formation in 3D magnetic configurations containing null-points and/or singular lines of the X-type. Formation of current sheets is revealed to occur in various 3D configurations, both with and without isolated magnetic null-points, specifically in configurations with X-lines. Local characteristics of 3D magnetic configuration define the parameters of the current sheet, which forms usually a twisted surface with an angular orientation determined by a local value of the transverse magnetic field gradient. A degree of plasma compression into the sheet decreases with a rise of longitudinal magnetic field component, displaying a transition to a behavior of uncompressible plasma. It is established that current sheet formation and magnetic reconnection processes can take place within a limited range of initial conditions, while a gradient of transverse magnetic field is the most important parameter.