Understanding the variability of nightside temperatures, NO UV and O2 IR nightglow emissions in the Venus upper atmosphere

Venus Express ( VEX) has been monitoring key nightglow emissions and thermal features (O-2 IR nightglow, NO UV nightglow, and nightside temperatures) which contribute to a comprehensive understanding of the global dynamics and circulation patterns above similar to 90 km. The nightglow emissions serve as effective tracers of Venus' middle and upper atmosphere global wind system due to their variable peak brightness and horizontal distributions. A statistical map has been created utilizing O-2 IR nightglow VEX observations, and a statistical map for NO UV is being developed. A nightside warm layer near 100 km has been observed by VEX and ground-based observations. The National Center for Atmospheric Research (NCAR) Venus Thermospheric General Circulation Model (VTGCM) has been updated and revised in order to address these key VEX observations and to provide diagnostic interpretation. The VTGCM is first used to capture the statistically averaged mean state of these three key observations. This correspondence implies a weak retrograde superrotating zonal flow (RSZ) from similar to 80 km to 110 km and above 110 km the emergence of modest RSZ winds approaching 60 m s(-1) above similar to 130 km. Subsequently, VTGCM sensitivity tests are performed using two tuneable parameters ( the nightside eddy diffusion coefficient and the wave drag term) to examine corresponding variability within the VTGCM. These tests identified a possible mechanism for the observed noncorrelation of the O-2 and NO emissions. The dynamical explanation requires the nightglow layers to be at least similar to 15 km apart and the retrograde zonal wind to increase dramatically over 110 to 130 km.