NOTE TO REPORTERS AND EDITORS: Story embargoed for release until 2 p.m. PST on Monday, December 10, 2001 Researchers have known for three decades that the Earth is a tremendous radio transmitter, but they were never able to pinpoint where the noise was coming from. Using the quartet of spacecraft from the Cluster mission, scientists have been able to precisely locate the sourse of that radio noise along magnetic field lines several thousand miles above bright regions in the aurora. In another finding, researchers using instruments on Cluster have made the first close-up measurements of the formation of electrical structures known as the "black aurora," comparable to a photographic negative of the aurora. Researchers have found evidence of electrons being accelerated away from the upper atmosphere into space, creating holes in the ionosphere. NASA Press Release: Cluster Tunes Into Earth^(1)s Frequency, Pinpoints Location of Auroral Radio Emissions ESA Press Release: Cluster Quartet Probes the Secrets of the Black Aurora ESA Public Page about the black aurora . Images and movies from the press conference Audio-visual (Shockwave) clip of Auroral Kilometric Radio (AKR) burst emission received on Cluster spacecraft 1 (Rumba) and 3 (Samba) at 02:14 UT on July 28, 2001 Listen to the sounds of the aurora and magnetosphere Click here for a PDF version of "Temporal evolution of the electric field accelerating electrons away from the auroral ionosphere" by G.T. Marklund et al, to be published in Nature on December 13. Presentations related to this news, delivered at a press conference at the Fall Meeting of the American Geophysical Union The Cluster Mission, by Philippe Escoubet Cluster WBD Mutli-Spacecraft Observations of Auroral Kilometric Radiation, by Robert Mutel Evolution of Electric Fields in the Auroral Return Current Region, by Goran Marklund Background information on auroras and the Cluster Mission