Jovian x-ray emission from solar x-ray scattering

Soft x-ray emissions with brightnesses of about 0.01-0.2 Rayleighs have bee n 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 fo r low-latitude x-ray emission: (1) elastic scattering of solar x-rays by at mospheric neutrals, (2) fluorescent scattering of carbon K-shell x-rays fro m methane molecules located below the jovian homopause. Our modeled brightn esses agree, up to a factor of two, with the bulk of low-latitude ROSAT mea surements. This suggests that solar photon scattering (approximately 90 % e lastic scattering) may act in conjunction with energetic heavy ion precipit ation to generate jovian equatorial x-ray emission.