Vol 57, No 3 (2023)

This research studies the O2 (a1 Δg) nightglow distribution in 1.27 μm to understand the dynamics of the atmosphere of Venus. Several factors were considered in the retrieval process, such as thermal emission of the lower atmosphere, reflection by the clouds. Results show deviation from SS-AS circulation mode: the area where horizontal flows from the dayside converge and where oxygen recombines and emits shifts from the midnight to 22–23 hours local time. This shift is caused by solar-induced thermal tide on Venus nightside. Some conclusions about the upper mesosphere dynamics are also presented.

Venus has always been one of the priorities of the space research program in Russia. The history of successful investigations of Venus in the Soviet Union is primarily associated with delivering a whole series of spacecraft to it and implementing the first ever landing on its surface. In the last few years, the study of Venus in astrobiological direction has been rapidly developing. To date, a fairly large number of theoretical papers have been published, the main purpose of which is to estimate the possibility of the existence of living organisms on Venus. The most likely ecosystem, in which Earth-type organisms could develop, is considered to be a dense cloud layer of Venus. It is supposed that, in this layer, hypothetical microbial communities could exist in aerosols being a concentrated aqueous solution of sulfuric acid. Microorganisms in such a specific air habitat are to be exposed to several extreme factors at once, the main among which are very low values of pH and water activity. The principal strategies for survival under these conditions should be the availability of effective biochemical mechanisms of resistance to the impact of adverse environmental factors and the use of all possible ways of extracting energy in such an ecosystem to maintain the biomass of organisms at a level for stable reproduction.

Within the problem of modeling the evolution of a protostellar disk, a discussion is presented on the effect of radiation on the Jeans gravitational instability for a self-gravitating optically thick (for intrinsic infrared radiation) gas-and-dust medium, taking into account the influence of radiation pressure perturbations and radiative diffusion transfer on the critical wavelength. Two radiative diffusion approximations are considered: the case of perfect thermal equilibrium with the same temperature of matter and radiation and the case of the time dependence of the radiation field with an energy separation between radiation and matter. An analysis of the normal regime of modes is used to derive dispersion relations, which enable the derivation of modifications of the classical Jeans instability criterion under the influence of radiation pressure and radiation diffusion. In particular, it is shown that, in contrast to the system’s local thermodynamic equilibrium, where the acoustic velocity of perturbed gas propagates with the isothermal speed of sound, in the case of different temperatures of radiation and gas, the perturbing wave propagates with the adiabatic speed of sound in gas. The results obtained are aimed at solving the problem of gravitational instability of individual massive protostellar disks or self-gravitating radiative media characterized by large optical depths for their dust-transformed intrinsic infrared radiation.

Measurements of ion velocity distributions are one of basic goals of space plasma studies. There is variety of ion and electron spectrometers (see, for example, Wüest et al., 2007; Young et al., 2007; Zurbuchen and Gershman, 2016; Vaisberg et al., 2016). The most commonly used ion spectrometer is the top-hat analyzer (Carlson et al., 1983) consisting of a toroidal electrostatic analyzer, an electrostatic scanner, and a timeof-flight section with thin foil as a start element and ion preacceleration. We describe a new energy-mass analyzer with an electrostatic scanner providing a hemispheric field of view with small aberration, a toroidal electrostatic analyzer, and a time-of-flight synchronizer with a simple gate. It provides desirable hemisphere scanning, wide energy range, and reasonable mass resolution to meet most space exploration challenges. It can provide detailed measurements of the ion velocity distribution of ion species without significant gaps to obtain the structure of the hot plasma flow. With simple electrooptics elements this analyzer can be easily modified for many plasma research purposes.