Magnetic field line reconnection experiments, 3. Ion acceleration, flows, and anomalous scattering

Abstract

Extensive spatial and temporal measurements of plasma pressure nkT e , magnetic force density J × B , and ion velocities v have been performed in a laboratory experiment undergoing magnetic field line reconnection. The pressure is found to peak at the two edges of the neutral sheet. It exhibits large transverse gradients, causing space charge fields and Hall currents. The magnetic force density arises mainly from induced axial neutral sheet currents and transverse magnetic fields but also from transverse currents and a magnetic field component along the separator. The total force density on the fluid, J × B ‐ ▽ p , is compared with direct measurements of the fluid acceleration by using differential particle detectors. It is found that the ion acceleration is strongly modified by scattering off wave turbulence. After several Alfvén times the fluid develops the classic flow pattern, with jetting from the edges of the neutral sheet to velocities close to the Alfvén speed.