Alexander S. Medvedev’s research while affiliated with Max Planck Institute for Solar System Research and other places

Observations of vibrationally excited hydroxyl (OH*) emissions are widely used to obtain information about the dynamics and composition of the atmosphere. We present some analytical approximations for the characteristics of the hydroxyl layer in the Martian atmosphere such as OH* concentration at the maximum and height of the maximum, as well as relations for estimating the influence of various factors on the OH* layer in night conditions. These characteristics depend on the temperature of the environment, concentration of atomic oxygen, and their vertical gradients. The relations are applied to the results of numerical modeling using the global atmospheric circulation model for prediction of seasonal behavior of the hydroxyl layer on Mars. Annual and intra-annual variations in the concentration of excited hydroxyl and layer height from the modeling data have both some similarities with those of the Earth and significant differences. The concentration and height maximum in the equatorial, northern and southern midlatitudes vary depending on the season; the maximum concentration and the minimum height fall on the first half of the year. Model calculations confirmed the presence of the peak OH* concentration at polar latitudes in winter at an altitude of approximately 50 km with the volume emission densities of 2.1, 1.4, and 0.6 × 104 photons cm–3 s–1 for vibrational level transitions 1–0, 2–1, and 2–0, respectively. The relations obtained may be used for the analysis of measurements and interpretation of their variations.

Gravity waves are primarily generated in the lower atmosphere, and can reach thermospheric heights in the course of their propagation. This paper reviews the recent progress in understanding the role of gravity waves in vertical coupling during sudden stratospheric warmings. Modeling of gravity wave effects is briefly reviewed, and the recent developments in the field are presented. Then, the impact of these waves on the general circulation of the upper atmosphere is outlined. Finally, the role of gravity waves in vertical coupling between the lower and the upper atmosphere is discussed in the context of sudden stratospheric warmings.