Discovery of Soft X-Ray Emission from Io, Europa and the Io Plasma Torus

Abstract

We report the discovery of soft (0.25--2 keV) x-ray emission from the Galilean satellites Io and Europa, probably Ganymede, and from the Io Plasma Torus (IPT). Bombardment by energetic (>10 keV) H, O, and S ions from the region of the IPT seems the likely source of the x-ray emission from the Galilean satellites. According to our estimates, fluorescent x-ray emission excited by solar x-rays, even during flares from the active Sun, charge-exchange processes, previously invoked to explain Jupiter's x-ray aurora and cometary x-ray emission, and ion stripping by dust grains fail to account for the observed emission. On the other hand, bremsstrahlung emission of soft X-rays from non-thermal electrons in the few hundred to few thousand eV range may account for a substantial fraction of the observed x-ray flux from the IPT.

7 pages, 4 figures, accepted by The Astrophysical Journal

References in corpus (2)

• Chandra X-Ray Observatory (CXO):Overview
• Mitigating Charge Transfer Inefficiency in the Chandra X-ray Observatory's ACIS Instrument

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