Several classes or types of coronal transients are believed to originate near the solar surface at the base of pre-existing coronal magnetic loops. These loops often lie beneath an overlying open-field region in a typical coronal- or helmet-streamer configuration. Recent experimental results indicate that these pre-existing magnetic loops may be torn open by the explosive force of the solar phenomena responsible for the transient. Numerical solutions of the time-dependent, two-dimensional, dissipationless, MHD equations of motion (the equations are discussed by Steinolfson et al. (1978)) are used to examine the formation of a coronal streamer magnetic structure and the evolution of the streamer following an explosive solar event in the closed-field region.