Physics
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufm.p33a1271h&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #P33A-1271
Physics
[0300] Atmospheric Composition And Structure, [0310] Atmospheric Composition And Structure / Airglow And Aurora, [5405] Planetary Sciences: Solid Surface Planets / Atmospheres, [6295] Planetary Sciences: Solar System Objects / Venus
Scientific paper
The O2-1.27 μm nightglow distribution, which has the peak intensity in the depression region of the day-to-night flow, gives us information of the wind field at about 95 km in Venus. The past nightglow observations [Crisp et al., 1996] showed that the intensity of the nightglow in the brightness region changed by 20 % in about one hour, and the brightness region disappeared in less than one day. The observation results obtained by Venus Express (VEX) also showed the temporal variations of the nightglow emission. Some simulation studies suggested contributions of gravity waves generated in the cloud deck (50-70 km) to the temporal variations. However, the causes of the temporal variations are still unknown. In recent years, the importance of planetary-scale waves for the dynamics of the Venusian atmosphere has been recognized. For example, Takagi and Matsuda [2006] suggested that the atmospheric superrotation was driven by the momentum transport due to the vertical propagation of the thermal tides generated in the Venus cloud deck. In order to estimate effects of the planetary-scale waves on the temporal variations of the nightglow, we have performed numerical simulations with a general circulation model (GCM), which includes the altitude region of 80 - about 200 km. The planetary-scale waves (thermal tides, Kelvin wave and Rosbby wave) are imposed at the lower boundary. The amplitudes and phase velocities of the waves are assumed from the study by Del Genio and Rossow [1990]. The nightglow intensity and its global distribution are calculated from the GCM results assuming the chemical equilibration. In this study, we investigate contributions of the planetary-scale waves on the temporal variations of the nightglow shown by past observations. In addition, we show the characteristics of the wave propagation and the interactions between the waves in the Venusian upper atmosphere. Venus Climate Orbiter (VCO), which will be launched in 2010 as the second Japanese planetary mission, is expected to provide precious information about the atmospheric waves at the cloud top (about 70 km) and the nightglow distributions in the thermosphere. We can understand effects of the atmospheric waves on the Venusian thermosphere quantitatively by performing simulations with new information about the atmospheric waves obtained from the detailed nightglow observations.
Fujiwara Hideaki
Hoshino N.
Kasaba Yasumasa
Takagi Masahiro
Takahashi Yoshiyuki
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