A current sheet is electric current within a (relatively) thin slice of a plasma cloud and is a feature of magnetohydrodynamics. The magnetic field of the Sun generates a large current sheet through the solar system (the heliospheric current sheet or HCS) that extends beyond Pluto yet is only about 10,000 km in thickness.
A current sheet generally has a higher density of electrons than the surrounding medium and typically a concave lens shape, causing electromagnetic radiation passing across it to diverge. But magnetic reconnection within a sheet (a reconnection sheet) can create heat, spreading electrons to a lower density, creating to a convex optical lens and convergence of electromagnetic rays. A sheet with such "bumps" can offer multiple points where an observer is in the line of sight of an object beyond the sheet, leading to scintillation at points, and usable as a cosmic lens (as in scintillometry).