New clues about magnetosphere noise and black aurora



The noise sounds vaguely as if it emanates from the high-pitched chatter of tropical birds or wetted fingers rubbing along musical glasses. However, the auroral kilometric radiation (AKR)—a radio wave of about 540–550 kilohertz just below the AM radio band—emanates from Earth's magnetosphere 11,000–13,000 kilometers above the Earth's northern lights.

Some researchers had proposed this as the likely origin for the noise three decades ago. However, scientists at the AGU Fall Meeting, held in San Francisco, California, said that new measurements made by instruments onboard the four spacecraft of the European Space Agency's (ESA) Cluster mission have confirmed this theory.