TRANSIENT DECREASES OF EARTHS FAR-ULTRAVIOLET DAYGLOW

Ten years ago transient decreases in Earth's far-ultraviolet dayglow w ere reported for global images acquired with the high-altitude, polar- orbiting spacecraft Dynamics Explorer 1. These decreases were observed primarily in the atomic oxygen emissions at 130.4 nm. The diameters o f these dark spots, or ''atmospheric holes'', were in the range of 50 to 100 km. Recently a sophisticated camera for imaging Earth's far-ult raviolet dayglow, with far greater spatial and temporal resolutions th an its predecessor, was launched with the Polar spacecraft. The images from this spacecraft provide irrefutable evidence that these atmosphe ric holes are a geophysical phenomenon.