[en] 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.
Disciplines :
Earth sciences & physical geography
Author, co-author :
Elsner, Ronald F.; NASA Marshall Space Flight Center > Space Science Department
Gladstone, G. Randall; Southwest Research Institute > Department of Space Science
Waite, J. Hunter; University of Michigan > Department of Atmospheric, Oceanic and Space Sciences
Crary, Frank J.; University of Michigan > Department of Atmospheric, Oceanic and Space Sciences
Howell, Robert R.; University of Wyoming > Department of Physics and Astronomy
Johnson, Robert E.; University of Virginia > Department of Engineering Physics
Ford, Peter G.; Massachusetts Institute of Technology > Center for Space Research
Metzger, Albert E.; Jet Propulsion Laboratory (Pasadena)
Hurley, Kevin C.; University of California at Berkeley > Space Science Laboratoy
Feigelson, Eric D.; Pennsylvania State University
Garmire, Gordon P.; Pennsylvania State University
Bhardwaj, Anil; Vikram Sarabhai Space Centre > Space Physics Laboratory
Grodent, Denis ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)
Majeed, Tariq; Southwest Research Institute > Department of Space Science
Tennant, Allyn F.; NASA Marshall Space Flight Center > Space Science Department
Weisskopf, Martin C.; NASA Marshall Space Flight Center > Space Science Department