Stratospheric benzene and hydrocarbon aerosols detected in Saturn's auroral regions

摘要: Context. Saturn’s polar upper atmosphere exhibits significant auroral activity; however, its impact on stratospheric chemistry (i.e. the production of benzene and heavier hydrocarbons) thermal structure remains poorly documented. Aims. We aim to bring new constraints distribution in stratosphere, characterize aerosols (their vertical distribution, composition, infrared optical properties), quantify aerosols’ radiative structure. Methods. Infrared spectra acquired by Composite Spectrometer (CIRS) board Cassini limb viewing geometry are analysed derive column abundances aerosol opacity profiles over 3 0.1 mbar pressure range. The spectral dependency haze is assessed ranges 680–900 1360–1440 cm −1 . Then, a climate model used compute equilibrium temperature profiles, with without haze, given properties derived from CIRS measurements. Results. On region (80 ◦ S), found be slightly enhanced compared equatorial mid-latitude values. This contrasts Moses & Greathouse (2005, J. Geophys. Res., 110, 9007) photochemical model, which predicts abundance 50 times lower at 80 S than equator. advocates for inclusion ion-related reactions chemical models. stratosphere also enriched aerosols, signatures consistent vibration modes assigned aromatic aliphatic hydrocarbons, presenting similarities observed Titan’s stratosphere. mass loading estimated 1−4 × 10 −5 gc m −2 , an order magnitude less Jupiter, weaker power Saturn. estimate that this warms middle 6 K summer cools 5 winter. Hence, linked activity can partly account warm hood