A new analytic expression is derived for the resonant drive of high n Alfvénic modes by ICRHaccelerated particles. This derivation includes finite orbit effects, and the foralism is completely non-perturbative. The high-n limit is used to calculate the complex particle response integrals along the orbits explicitly. This new theory is applied to downward sweeping Alfvén Cascade quasimodes completing the theory of these modes, and making testable predictions. These predictions are found to be consistent with experiments carried out on the Joint European Torus.