UV resonance line dayglow emissions on Earth and Jupiter

Atomic resonance line emissions have been used to probe the structure and composition of the upper regions of planetary atmospheres. In this paper the similarities and differences for some emissions of importance in the atmospheres of Earth and Jupiter are examined. For each planet both a conservative resonance line and a line for which there is a considerable branching ratio are considered. On Earth examples of important conservative and nonconservative resonance emissions are OI 1304 Å and OI 989 Å, respectively. Both of these features are excited by photoelectron impact on atomic oxygen. The OI 1304‐Å triplet has an additional source due to resonant scattering of the solar OI 1304‐Å emission feature. These emissions are typically observed from a much different perspective than corresponding emissions from other planets, usually from inside the atmosphere, at substantial line‐center optical depths. On Jupiter the brightest conservative resonance line is HI 1216Å (Lyman α), while HI 1026 Å (Lyman β) is an example of an important nonconservative resonance line. In this paper, models are presented for the intensities of these features as would be seen from a distance of several planetary radii, using the same geometry of observation for both Earth and Jupiter. The variations of the line‐integrated emissions across the disk and near the limb of each planet are examined in detail. Line profiles for the emissions near the limb and at disk‐center are also examined. The models reveal the importance of including inhomogeneities and temperature variations of the atmospheres in scattering models, and indicate that outer planet emissions previously interpreted as “electroglow” may be solely due to resonant scattering of solar emissions.