Dr. Waelbroeck works primarily on the macroscopic and mesoscopic dynamics of fusion plasmas.  He is the coauthor, with R. D. Hazeltine, of the textbook "The Framework of Plasma Physics." His research interests include magnetic reconnection, magnetic islands, the effect of flows on MHD modes, and the formulation of fluid closures. His main contributions include the demonstration that the formation of current ribbons in Sweet-Parker reconnection is a consequence of detailed helicity conservation; the discovery of the threshold condition for the onset of Sweet-Parker reconnection; the  growth rate of ballooning modes in the presence of flow shear; and the effect of the polarization currents in magnetic islands. Dr. Waelbroeck serves on the Board of Editors of Nuclear Fusion and chairs the fusion Theory Coordinating Committee.