NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Discovery of Soft X-Ray Emission from Io, Europa and the Io Plasma TorusThe Chandra X-ray Observatory observed the Jovian system for about 24 hours on 25-26 Nov 1999 with the Advanced CCD Imaging Spectrometer (ACIS), in support of the Galileo flyby of Io, and for about 10 hours on 18 Dec 2000 with the imaging array of the High Resolution Camera (HRC-I), in support of the Cassini flyby of Jupiter. Analysis of these data have revealed soft (0.25--2 keV) x-ray emission from the moons 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 the likely source of the x-ray emission from the Galilean moons. According to our estimates, fluorescent x-ray emission excited by solar x-rays is about an order of magnitude too weak even during flares from the active Sun to account for the observed x-ray flux from the IPT. Charge-exchange processes, previously invoked to explain Jupiter's x-ray aurora and cometary x-ray emission, and ion stripping by dust grains both fall by orders of magnitude. On the other hand, we calculate that bremsstrahlung emission of soft X-rays from non-thermal electrons in the few hundred to few thousand eV range accounts for roughly one third of the observed x-ray flux from the IPT. Extension of the far ultraviolet (FUV) IPT spectrum likely also contributes.
Document ID
20020019794
Acquisition Source
Marshall Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Elsner, R. F.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Gladstone, G. R.
(Southwest Research Inst. United States)
Waite, J. H.
(Michigan Univ. MI United States)
Crary, F. J.
(Michigan Univ. MI United States)
Howell, R. R.
(Wyoming Univ. Laramie, WY United States)
Johnson, R. E.
(Virginia Univ. VA United States)
Ford, P. G.
(Massachusetts Inst. of Tech. MA United States)
Metzger, A. E.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Hurley, K. C.
(California Univ. Berkeley, CA United States)
Feigelson, E. D.
(Pennsylvania State Univ. PA United States)
Six, N. Frank
Date Acquired
August 20, 2013
Publication Date
January 1, 2001
Subject Category
Lunar And Planetary Science And Exploration
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

Available Downloads

There are no available downloads for this record.
No Preview Available