By means of EUV absorption analysis as applied to the occultation method, vertical density profiles (200-400 km) of atomic oxygen have been derived for the mission period of the German-U.S. aeronomy satellite Aeros. One event, the geomagnetic disturbance of January 19-20, 1973, has been analyzed in more detail: (1) There is a time lag between the increase of the Kp index and atomic oxygen, which is greatest for lower heights. (2) The initial relative density increase is smaller for greater heights. (3) The relative increase is more pronounced for greater heights. (4) Two maximums of Kp are followed by two maximums of density. (5) The greater the relative increase of geomagnetic activity, i.e., of ΔKp, the higher the increase in density.