AMHERST, Mass. - For the first time, engineers and scientists have a reliable way to estimate the number of "sprites" spawned by a single thunderstorm. Sprites, the luminous red glows that are the high-altitude companions of some lightning strikes, are the focus of a new study by Steven Reising, assistant professor of electrical and computer engineering at the University of Massachusetts, along with Umran Inan and Timothy Bell of Stanford University in California. The team''s findings appear in the April 1 issue of Geophysical Research Letters (GRL), which is published by the American Geophysical Union. The work was funded by NASA, the U.S. Air Force, and the National Science Foundation.