Variability of the nitric oxide nightglow at Venus during solar minimum

Abstract : We present results from a NO airglow inversion method based on Venus Express data acquired from 2006 to 2010, during the last solar minimum period. We retrieve an altitude of 114 ± 10 km for the emission peak of the NO layer, with an associated scale height of 20 ± 10 km and an average limb brightness of 59.3 kR with a standard deviation of 63 kR. The inversion method allows for the quantification of the horizontal homogeneity of the NO layer. Images of the SPICAV field of view show a great variability of airglow morphologies, with NO layers that can be horizontally homogenous and continuous over distances exceeding 100 km, as well as sporadic patches of NO on a smaller horizontal scale. Frequent secondary emissions seen at lower tangent altitudes are the signatures of the complex dynamics of the upper Venusian atmosphere.