Observation of the potential well at the neutral sheet and its effects on ion dynamics during magnetic reconnection in MRX*

Radial floating potential profiles have been obtained through the use of floating potential probes and Langmuir probes. Similar to those seen in numerical simulations and space observations, potential wells develop across the diffusion region during ``Pull'' reconnection in the Magnetic Reconnection Experiment (MRX). The potential well becomes deeper and broader further downstream. The magnitude of the potential drop is 10- 15V at the center and 15-35V downstream. A downstream-pointing electric field of 300-700 V/m is also measured. The magnitude of this potential well is related to the dip in the sum of magnetic pressure and electron pressure, indicating ions are heated by the in-plane electric field. In-plane ion flow profiles are measured by Mach probes to verify ion energy gain from in-plane electric field.