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Detailed Reference Information |
Bhardwaj, A., Elsner, R.F., Gladstone, G.R., Waite, J.H., Branduardi-Raymont, G., Cravens, T.E. and Ford, P.G. (2006). Low- to middle-latitude X-ray emission from Jupiter. Journal of Geophysical Research 111: doi: 10.1029/2006JA011792. issn: 0148-0227. |
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The Chandra X-ray Observatory (CXO) observed Jupiter during the period 24--26 February 2003 for ~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 ~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 ~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. |
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Abstract |
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Keywords
Planetary Sciences, Comets and Small Bodies, Atmospheres, Planetary Sciences, Comets and Small Bodies, Magnetospheres, Planetary Sciences, Solar System Objects, Jupiter, Solar Physics, Astrophysics, and Astronomy, X-rays, gamma rays, and neutrinos |
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Publisher
American Geophysical Union 2000 Florida Avenue N.W. Washington, D.C. 20009-1277 USA 1-202-462-6900 1-202-328-0566 service@agu.org |
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