Hydrocarbon Photochemistry and Lyman Alpha Albedo of Jupiter

A combined study of hydrocarbon and atomic hydrogen photochemistry is made to calculate self-consistently the Loc albedo of Jupiter. It is shown that the Loc emissions observed by Voyagers I and //can be explained by resonance scattering of sunlight. Precipitation-of energetic particles from the magnetosphere can provide the large required source of atomic hydrogen, although the contribution of direct particle excitation to the disk-averaged brightness is insignificant. The variability of the Loc brightness inferred from many observations in recent years is examined. The large difference in the brightness of the He 584 A resonance line observed by Pioneer and Voyager is briefly discussed. Driving the photochemistry by solar ultraviolet radiation alone yields a maximum mixing ratio of C2H 6 + C2H 2 at 102 atm of about 4 x 106 . The possibility of additional CH4 dissociation from precipitation of magnetospheric particles is discussed. The photochemistry of C2 H 2 and C2H 3 is sufficiently uncertain not to permit accurate calculations of their densities and the ratio C2 H6/C2H 2 . Subject headings: molecular processes planets: abundances planets: Jupiter