The lack of evidence for magnetic disconnection of coronal mass ejections (CMEs) from the Sun has long been a puzzle, as it implies a buildup of the interplanetary magnetic field (IMF) magnitude over time. Such a buildup is ruled out by observations. Magnetic reconnection above helmet streamer configurations could provide a mechanism for maintaining the observed relative constancy of the IMF [McComas et al., 1989>; McComas et al. [1991> showed observational evidence of reconnection above a streamer. We investigate this interpretation using time-dependent MHD simulations. We model the opening of new magnetic flux on the Sun (as might occur in a CME or other transient event) as an increase in magnetic flux at the poles of a simulated corona. We find that this perturbation can in fact cause reconnection above an equatorial helmet streamer, and the resultant density signature is similar to the observations of McComas et al. [1991>. ¿ American Geophysical Union 1992