Solar System Studies
The Jovian and Saturian Systems
X-ray studies of Jupiter's auroral zones near the north and south poles, where the X-ray emission is most intense, offer a probe of Jupiter's magnetosphere (see the review by Bhardwaj and Gladstone 2000). Chandra and XMM-Newton data show that this auroral emission is due to the precipitation of highly ionized oxygen and either sulfur (favored by Chandra) or carbon (favored by XMM) into the polar regions (Horanyi et al. 1988, Cravens et al. 1995, 2003); the ionization states present and the line characteristics provide information on the electric fields present, thus probing the polar magnetosphere dynamics. Oscillations in the northern auroral flux observed in December 2000 (Gladstone et al. 2002) are likely associated with the energetic particle flux in the outer disk magnetosphere and with quasiperiodic radio bursts from Jupiter (McKibben, Simpson and Zhang 1993, MacDowall et al. 1993, Karanikola et al. 2004). More detailed observations of these oscillations and the conditions under which they appear would further constrain the dynamics of Jupiter's polar magnetosphere.
Chandra discovered faint X-ray emission from the Io plasma torus and Io, Europa, and possibly Ganymede (Elsner et al. 2002). While the origin of the X-ray emission from the torus in not clear, the emission from the Galilean moons is almost certainly due to bombardment of their surfaces by energetic hydrogen, oxygen, and sulfur atoms and ions.
Chandra observations of Saturn found variations in the averaged X-ray flux of a factor of ~4 over one week (Bhardwaj et al. 2005) that appeared closely tied to the incident solar X-ray flux. In addition, on timescales of ~0.5 hour, an X-ray "flare" from Saturn was closely linked to the eruption of a solar X-ray flare. The same observations showed emission from the south polar cap and an emission line probably due to oxygen Ka fluorescence from the rings. These new objects are faint X-ray sources, and detailed investigation of their X-ray properties require the high-throughput and highenergy resolution provided by Constellation-X.
References
Bhardwaj, A., and Gladstone, G. R., 2000, Rev. Geophys., 38, 295Bhardwaj, A., et al., 2005, in preparation
Cravens, T. E., Howell, E., Waite, J. H., and Gladstone, G. R., 1995, J. Geophys. Res., 100, 17, 153
Cravens, T. E., et al., 2003, J. Geophys. Res., 108
Elsner, R. F., et al., 2002, ApJ, 572, 1077
Gladstone, G. R., et al., 2002, Nature, 415, 1000
Horanyi, M., Cravens, T. E., and Waite, J. H., 1988, J. Geophys. Res., 93, 7251
Karanikola, I., Athanasiou, M., Anagnostopoulos, G. C., Pavlos, G. P., and Preka-Papadema, P., 2004, Planet Space Sci., 52, 543
MacDowall, R. J., et al., 1993, Planet. Space Sci., 41, 1059
McKibben, R. B., Simpson, J. A., and Zhang, M., 1993, Planet Space Sci., 41, 1041
