We present an observational study of the global dynamics of the plasmasphere, aurora, ring current, and subauroral ionosphere on 17 April 2002 during a substorm. Global observations by the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) and in situ observations by DMSP F13 provide a comprehensive view of the coupled response of the inner magnetosphere and ionosphere. At 1900 UT a substorm onset initiated a sunward convective impulse, which caused a ring current injection. The motion of this impulse past the plasmasphere caused ripples to propagate along the plasmapause, eastward and westward from premidnight magnetic local time (MLT). The motion of the ripples agrees exceptionally well with the motion of the aurora and the ring current, implying strong coupling. The westward moving ripple (on the duskside) participated in a two-phase plasmapause undulation effect. In the first phase (1915 UT to 1936 UT), a mild 0.4--0.5 RE bulge formed near 2000 MLT, probably caused by an E-field induced by local reduction of the magnetic field by the ring current pressure increase. In the second phase (1936 UT to 2037 UT) this mild bulge was removed by a subauroral polarization stream (SAPS) westward flow that stripped away the outer 1 RE of the duskside plasmasphere. The SAPS effect was observed in the ionosphere by DMSP between about 1930 UT and 2000 UT and is evident in vector E-fields inferred from plasmapause motion. All the observations of this event suggest strong coupling among the plasma populations of the magnetosphere-ionosphere system. This event represents the first identification of the directly observed global plasmaspheric effects of a substorm-driven impulse, the SAPS flow channel, and the ring-current magnetic field reduction.