The MU radar was used to observed the ionospheric F-region electron density simultaneously in four oblique beams during the geomagnetic storm of 20--23 October 1989, when the first significant auroral display over Japan since 1963 was observed. The four beams, separated by about 250 km horizontally in the F region, observed drastically different behavior, with independent and extreme changes occurring on time scales of one minute during the period of peak activity, indicating a strongly structured ionosphere streaming over the radar. We observed cases in which, simultaneously, a deep trough was seen in one beam, densities exceeding 4¿106 cm-3 were seen in another, and a normal ionosphere was seen in a third. During the most disturbed periods the F-layer peak height appeared to rise to 800 km altitude in one beam while it remained near 500 km in another. ¿ American Geophysical Union 1991