Scientists have obtained new insight into the unique power source for many of Jupiters auroras, the most spectacular and active auroras in the Solar System. Extended monitoring of the giant planet with NASAs Chandra X-ray Observatory detected the presence of highly charged particles crashing into the atmosphere above its poles.
Jupiter shows intense X-ray emission associated with auroras in its polar regions (Chandra image on left). Extended monitoring by Chandra showed that the auroral X-rays are caused by highly charged particles crashing into the atmosphere above Jupiters poles. The charged particles were primarily ions of oxygen and other elements that were stripped of most of their electrons, which implies that the ions were accelerated to high energies in a multimillion-volt environment above the planets poles. Such high voltages indicate that the cause of many of Jupiters auroras is different from auroras produced on Earth or Saturn. The accompanying schematic illustrates how Jupiters unusually frequent and spectacular auroral activity is produced. Jupiters strong, rapidly rotating magnetic field (light blue lines) generates strong electric fields in the space around the planet. Particles (white dots) from Jupiters volcanically active moon, Io, drift outward to create a huge reservoir of electrons and ions. These charged particles, trapped in Jupiters magnetic field, are continually being accelerated (gold particles) down into the atmosphere above the polar regions, so auroras are almost always active on Jupiter. Electric voltages of about 10 million volts, and currents of 10 million amps - a hundred times greater than the most powerful lightning bolts - are required to explain the auroras, which are a thousand times more powerful than those on Earth. On Earth, auroras are triggered by solar storms of energetic particles, which disturb Earths magnetic field. As shown by the swept-back appearance in the illustration, gusts of particles from the Sun also distort Jupiters magnetic field, and on occasion produce auroras. Credit: NASA/CXC/MSFC/R. Elsner et al.
X-ray spectra measured by Chandra showed that the auroral activity was produced by ions of oxygen and other elements that were stripped of most of their electrons. This implies that these particles were accelerated to high energies in a multimillion-volt environment above the planets poles. The presence of these energetic ions indicates that the cause of many of Jupiters auroras is different from auroras produced on Earth or Saturn.
"Spacecraft have not explored the region above the poles of Jupiter, so X-ray observations provide one of the few ways to probe that environment," said Ron Elsner of the NASA Marshall Space Center in Huntsville, Alabama, and lead author on a recently published paper describing these results in the Journal for Geophysical Research. "These results will help scientists to understand the mechanism for the power output from Jupiters auroras, which are a thousand times more powerful than those on Earth."
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