Sometimes the puppets control the puppeteer, volcanic outbursts on Jupiter's moon lo pull the strings for brilliant auroras on its parent planet. Auroras are caused when charged particles hit a planefs magnetic field. Jupiter has a permanent ring of auroral light on each of its poles, and lo's volcanoes have long been thought the source of most of the particles responsible for the light show. However, variations in the rings were suspected to be a result of pressure changes in the solar wind. New observations suggest lo can control these changes as well, say Bertrand Bonfond of the University of Liege in Belgium and colleagues. They observed Jupiter and lo with the Hubble Space Telescope once a day between February and June 2007 and saw Jupiter's auroral rings widen mysteriously In that time.
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