Jovian x-ray emission from solar x-ray scattering

Soft x-ray emissions with brightnesses of about 0.01-0.2 Rayleighs have been observed from both the equatorial and auroral regions of Jupiter. It has been proposed that the equatorial emission, like the auroral emission, may be largely due to precipitation of energetic heavy ions into the atmosphere [Waite et al., 1997]. In this paper we model two alternative mechanisms for low-latitude x-ray emission: (1) elastic scattering of solar x-rays by atmospheric neutrals, (2) fluorescent scattering of carbon K-shell x-rays from methane molecules located below the jovian homopause. Our modeled brightnesses agree, up to a factor of two, with the bulk of low-latitude ROSAT measurements. This suggests that solar photon scattering (approximately 90 % elastic scattering) may act in conjunction with energetic heavy ion precipitation to generate jovian equatorial x-ray emission.