Anomalous increases of the ionization density at middle latitudes (positive ionospheric storms) and anomalous increases of the neutral gas density at low latitudes (the geomagnetic activity effect) are promient features of upper atmospheric storms. The present study investigates the idea that both phenomena are caused by traveling atmospheric disturbances (TADs). According to theory, such TADs are generated during magnetic substorm activity and propagate with velocity from polar to equatorial latitudes. To examine the above hypothesis, magnetic, ionospheric, and neutral atmospheric data are compared for five different disturbance events. These case studies demonstrate that (1) there is is a good temporal correlation between magnetic substorm activity at high latitudes, daytime positive ionospheric storms at middle latitudes, and the geomagnetic activity effect at low latitudes; (2) the initial phase of positive ionospheric storms propagates with high velocity toward lower latitudes; (3) this velocity is roughly consistent with the time lag of the geomagnetic activity effect at low latitudes; (4) the ionpsheric disturbances is a conjugate phenomenon of global extent; and (5) it cannot be explained as an electric field effect. In summary, our data are fully consistent with the idea that TADs are responsible for both positive ionospheric storms at middle latitudes and the geomagnetic activity effect at low latitudes. ¿American Geophysical Union 1993