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Low- to Middle-Latitude X-Ray Emission from JupiterThe Chandra X-ray Observatory (CXO) observed Jupiter during the period 24-26 February 2003 for approx. 40 hours (4 Jupiter rotations), using both the spectroscopy array of the Advanced CCD Imaging Spectrometer (ACIS-S) and the imaging array of the High-Resolution Camera (HRC-I). Two ACIS-S exposures, each -8.5 hours long, were separated by an HRC-I exposure of approx. 20 hours. The low- to middle-latitude nonauroral disk X-ray emission is much more spatially uniform than the auroral emission. However, the low- to middle-latitude X-ray count rate shows a small but statistically significant hour angle dependence and depends on surface magnetic field strength. In addition, the X-ray spectra from regions corresponding to 3-5 gauss and 5-7 gauss surface fields show significant differences in the energy band 1.26-1.38 keV, perhaps partly due to line emission occurring in the 3-5 gauss region but not the 5-7 gauss region. A similar correlation of surface magnetic field strength with count rate is found for the 18 December 2000 HRC-I data, at a time when solar activity was high. The low- to middle-latitude disk X-ray count rate observed by the HRC-I in the February 2003 observation is about 50% of that observed in December 2000, roughly consistent with a decrease in the solar activity index (F10.7 cm flux) by a similar amount over the same time period. The low- to middle-latitude X-ray emission does not show any oscillations similar to the approx. 45 min oscillations sometimes seen from the northern auroral zone. The temporal variation in Jupiter's nonauroral X-ray emission exhibits similarities to variations in solar X-ray flux observed by GOES and TIMED/SEE. The two ACIS-S 0.3-2.0 keV low- to middle-latitude X-ray spectra are harder than the auroral spectrum and are different from each other at energies above 0.7 keV, showing variability in Jupiter's nonauroral X-ray emission on a timescale of a day. The 0.3-2.0 keV X-ray power emitted at low to middle latitudes is 0.21 GW and 0.39 GW for the first and second ACIS-S exposures, respectively. We suggest that X-ray emission from Jupiter's disk may be largely generated by the scattering and fluorescence of solar X rays in its upper atmosphere, especially at times of high incident solar X-ray flux. However, the dependence of count rate on surface magnetic-field strength may indicate the presence of some secondary component, possibly ion precipitation from radiation belts close to the planet.
Document ID
20070018752
Acquisition Source
Marshall Space Flight Center
Document Type
Other
External Source(s)
Authors
Bhardwaj, Anil
(Vikram Sarabhai Space Centre Trivandrum, India)
Elsner, Ronald F.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Gladstone, G. Randall
(Southwest Research Inst. San Antonio, TX, United States)
Waite, J. Hunter, Jr.
(Southwest Research Inst. San Antonio, TX, United States)
Branduardi-Raymont, Graziella
(University Coll. London, United Kingdom)
Cravens, Thomas E.
(Kansas Univ. Lawrence, KS, United States)
Ford, Peter G.
(Massachusetts Inst. of Tech. Cambridge, MA, United States)
Date Acquired
August 23, 2013
Publication Date
November 22, 2006
Publication Information
Publication: Journal of Geophysical Research
Volume: 111
ISSN: 0148-0227
Subject Category
Geophysics
Distribution Limits
Public
Copyright
Other

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