[en] We address several questions concerning the evolution of the chromoelectric flux tube connecting a (heavy) quark and antiquark as the distance between them increases. This is done in the continuum using a technique inspired by the QCD sum rule approach. Our main result is an analytic expression for the chromoelectric energy density valid at moderate distances. New estimates of the mass gap, string tension and Luescher coefficient are obtained. The radius squared of the flux tube is computed and seen to increase with the quark-antiquark separation. (orig.)