Effect of a magnetic field on plasma arcs at a liquid–air interface

This study investigates the impact of a time-varying axial magnetic field on the dynamics of plasma discharges at the liquid–air interface using conductive sodium chloride solutions. Generating the magnetic field using a Helmholtz coil reveals that the Lorentz force significantly alters the dynamics of the jet, stretching the vertical plasma jet horizontally, immediately, and rapidly converting it into horizontal arcs. Consequently, the formation of atmospheric plasmoids is prevented. Spectroscopic measurements reveal pronounced spatial variations in plasma emission: strong Balmer series emissions are observed near the cathode, shifting to dominant sodium and hydroxyl radical emissions at greater distances. Furthermore, magnetic field-induced lateral plasma motion generates distinct liquid surface flow patterns in the vicinity of the cathode. This paper clarifies the mechanism by which plasmoid formation is suppressed and highlights the potential of magnetic field control in applications involving precise plasma–liquid interactions.