  In Coulomb gauge there is a longitudinal color electric field associated with
a static quark-antiquark pair. We have measured the spatial distribution of
this field, and find that it falls off exponentially with transverse distance
from a line joining the two quarks. In other words there is a Coulomb flux
tube, with a width that is somewhat smaller than that of the minimal energy
flux tube associated with the asymptotic string tension. A confinement
criterion for gauge theories with matter fields is also proposed.
