We present the first clear and consistent evidence of solar wind drivers of Traveling Convection Vortices (TCVs). Using high time resolution data from GEOTAIL just upstream of the bowshock and within 10 earth radii of the sun-earth line, we were able to clearly identify solar wind triggers for 30 of 31 large amplitude TCV events during 1995. These data showed that 20 of the 30 solar wind drivers were isolated foreshock cavities of the type that have been previously reported. A further 8 events belong to a similar class which occurred primarily during rapid rotations of the IMF from or to a radial orientation, accompanied by a foreshock cavity-like region at the edge of the IMF transition. These observations suggest that the vast majority of TCVs are driven by perturbations of the magnetosphere caused by foreshock cavities that are formed in the interaction between the IMF and the bowshock.