Evolution of an arched magnetized laboratory plasma in a sheared magnetic field

Arched magnetized structures are a common occurrence in space and laboratory plasma. Results from a laboratory experiment on spatio-temporal evolution of an arched magnetized plasma ($\beta \approx 10^{-3}$, Lundquist number $\approx 10^{4}$, plasma radius/ion gyroradius $\approx 20$) in a sheared magnetic configuration have been discussed. The experiment is designed to model conditions relevant to formation and destabilization of similar structures in the solar atmosphere. The direction of a nearly horizontal overlying magnetic field was varied to study two different regimes of magnetic forces that assist or inhibit expansion of the arched plasma. The electrical current in the arched plasma was well below the current required to make it kink unstable. A significant increase in the writhe of the arched plasma and formation of a magnetized plasma jet were key observations when overlying magnetic field was oriented to inhibit its expansion.