Low- to middle-latitude X-ray emission from Jupiter

Bhardwaj, Anil ; Elsner, Ronald F. ; Gladstone, G. Randall ; Waite Jr., J. Hunter ; Branduardi-Raymont, Graziella ; Cravens, Thomas E. ; Ford, Peter G. (2006) Low- to middle-latitude X-ray emission from Jupiter Journal of Geophysical Research: Atmospheres, 111 (A11). A11225_1-A11225_16. ISSN 0148-0227

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Official URL: http://www.agu.org/pubs/crossref/2006/2006JA011792...

Related URL: http://dx.doi.org/10.1029/2006JA011792


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.

Item Type:Article
Source:Copyright of this article belongs to American Geophysical Union.
Keywords:Jupiter X Rays; Chandra X-ray Observatory; Solar X-ray Scattering and Spectrum; Magnetic Field Morphology
ID Code:2484
Deposited On:08 Oct 2010 07:12
Last Modified:19 Jan 2011 11:59

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