In 1993, Michael Taylor of Utah State University used an airglow imager to snap images of an undular bore at the US Air Force Maui Optical Station in Haleakala, Hawaii. After further inspection of the images several years later, researchers at the US Air Force Research Laboratory at Hanscom Air Force Base, Mass., have presented a strong case that these bores occurred about 50 miles above Earth's surface and far above the troposphere.