A remarkable set of all-sky images using the 630 nm airglow emission has been taken over the Arecibo Observatory in Puerto Rico. Wave-like structures at a height of about 250 km are commonly found to travel in the southwest direction at speeds ranging from 20--120 m/s. Most surprising is that geomagnetic activity seems to greatly amplify them, forming very intricate patterns of light and dark. Simultaneous observations using GPS satellite transmissions on one night reveal that dark regions are severely plasma depleted while bright regions have nighttime content as large as the full noontime ionosphere. This unexpected geomagnetic effect at mid-latitudes has implications for trans-ionospheric radiowave propagation and Space Weather. ¿ 2000 American Geophysical Union