Transient decreases of Earth's far‐ultraviolet dayglow

Ten years ago transient decreases in Earth's far‐ultraviolet dayglow were 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 of these dark spots, or “atmospheric holes”, were in the range of 50 to 100 km. Recently a sophisticated camera for imaging Earth's far‐ultraviolet dayglow, with far greater spatial and temporal resolutions than its predecessor, was launched with the Polar spacecraft. The images from this spacecraft provide irrefutable evidence that these atmospheric holes are a geophysical phenomenon.