Measurements of atmospheric density near 200 km from the Satellite Electrostatic Triaxial Accelerometer (SETA) experiment are used to delineate the temporal, seasonal-latitudinal, and day/night dependences of the response to magnetic storm-related perturbations in high-latitude energetic inputs. Five periods of geomagnetic activity are analyzed and yield consistent results which can be interpreted within the framework of recent thermosphere-ionosphere simulations by Fuller-Rowell et al. [1995>: In response to a change in magnetic activity level from quiet (Kp≈1--2) to active (Kp≈4--7) conditions, an increase in daytime (1030 LT) density of order 50--70% occurs between 60 and 80¿ geographic latitude in the summer hemisphere, with about half the maximum response in the winter hemisphere. This difference is mainly due to the difference in ionization/conductivity levels (and hence joule heating rates) between the hemispheres. On the dayside, penetration of the disturbance at about the 50% intensity level is realized at the equator, whereas in the winter hemisphere equatorward penetration is much weaker. These effects are connected with the prevailing solar-driven circulation; the net summer-to-winter meridional flow facilitates equatorward advection of the disturbance bulge in the summer hemisphere but hinders advection in the winter hemisphere. In both hemispheres the daytime component of the solar-driven diurnal circulation tends to oppose equatorward penetration to the same degree. However, on the nightside (2230 LT) penetration at nearly the 100% level of both summer and winter disturbance bulges are realized to within 20¿ of the geographic equator. This behavior is associated with the equatorward advection in both hemispheres consistent with the nighttime component of the solar-driven circulation. Comparisons with the MSISE90 model [Hedin, 1991> show it to capture the salient features of the daytime behavior but exhibits little day/night asymmetry, in contrast to the experimental results. ¿ American Geophysical Union 1996