An experiment on the National Spherical Torus Experiment (NSTX) was designed to test the theory that biased electrodes can affect the local scrape-off layer (SOL) by creating a strong radial E × B flow (Cohen and Ryutov 1997 Nucl. Fusion37 621). These electrodes were located near the outer midplane and were biased at up to ±90 V with respect to the local vacuum vessel ground. This biasing caused large changes in the local SOL profiles as measured by an array of Langmuir probes between the electrodes. A theory is presented which at least partially describes the experimental results.