University of Kansas

X-Ray Emission in the Solar System

X-ray emission has been observed from many objects throughout the solar system including the Sun, the Moon, the Earth, Jupiter, and comets. The initial discovery of X-rays from comet Hyakutake (Lisse et al., 1996) was surprising, and a number of explanations were put forth, including bremsstrahlung associated with hot electron collisions with cometary neutrals or ions, scattering or fluorescence of solar X-rays from cometary neutrals or from dust particles, and charge transfer of heavy solar wind ions with neutrals (Cravens, 1997). X-rays have also been observed both from Jupiter's auroral region as well as from low latitudes (Waite et al., 1997a,b). Again, a number of emission mechanisms have been proposed, including precipitation of energetic heavy ions from the magnetosphere (Cravens et al., 1995). Predictions of X-ray emission from Venus, Mars, and from interstellar neutrals in the heliosphere have also been made. The Space Physics group at the University of Kansas is working on X-ray emission in the solar system, and this web site includes a number of papers and preprints on this topic.

References: Cravens, T. E., J. Geophys. Res., 100, 17153 (1995); Cravens, T. E., Geophys. Res. Lett., 24, 105 (1997); Lisse, C., et al., Science, 274, 205 (1996); Waite, J. H., et al., Science, 276, 104 (1997a); Waite, J. H., et al., Adv. Space Res., 20, 243 (1997b).