We have studied the change in the cosmic-ray density caused by propagating solarwind disturbances (characterized by enhancement in velocity and decrease in diffusion coefficient) by solving the modulation equation formulated by Parker, Gleeson, and Axford. The independent variables are radial distance and particle energy. The passage of the region of the enhanced solar wind speed leaves behind it net heating of cosmic ray particles. The cosmic-ray density is reduced principally by the sweeping effect of the propagating solar wind disturbance, and the rigidity spectrum of the percentage reduction in density or intensity is roughly proportional to the rigidity dependence of the reciprocal of the diffusion coefficient D. If D is proportional to &bgr;P, the calculated spectrum is close to P-0.8, which is compatible with the observationally derived spectrum of the Forbush decrease. The density reduction is expected to be preceded by a weak precursory increase at higher energies (T>1 GeV) but by a precursory decrease at lower energies. The latter is the consequence of the particle heating by the solar wind disturbance, but it often seems to be masked by enhancement of particles of the solar origin.