Discovery of soft X-ray emission from IO, europa, and the IO plasma torus

Ronald F. Elsner, G. Randall Gladstone, J. Hunter Waite, Frank J. Crary, Robert R. Howell, Robert E. Johnson, Peter G. Ford, Albert E. Metzger, Kevin C. Hurley, Eric D. Feigelson, Gordon P. Garmire, Anil Bhardwaj, Denis C. Grodent, Tariq Majeed, Allyn F. Tennant, Martin C. Weisskopf

Research output: Contribution to journalArticlepeer-review

47 Scopus citations


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 (greater than 10 keV) H, O, and S ions from the region of the IPT seems to be 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 nonthermal 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.

Original languageEnglish (US)
Pages (from-to)1077-1082
Number of pages6
JournalAstrophysical Journal
Issue number2 I
StatePublished - Jun 20 2002

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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