Lunar Tides in the Mesopause Region Obtained from Summer Temperature of the Hydroxyl Emission Layer

Geomagnetism and Aeronomy - The summer mesopause region (altitudes of 82–92 km) is the coldest place in the Earth’s atmosphere; it is influenced by external effects, including lunar...     

Empirical model of variations in the emission of the Infrared Atmospheric system of molecular oxygen: 3. Temperature

Rotational temperatures of the 1.58-μm (0–1) band of the Infrared Atmospheric system of molecular oxygen (IRAO₂), measured in Zvenigorod (56° N, 36° E), are systematized and analyzed. An empirical dependence of variations in the temperature of the 1.58-μm emission on the solar zenith angle is derived. The use of parameters of the altitude distribution of emission intensity 1.27 μm of middle atmosphere temperature profiles, received from the AURA satellite, allowed for the study of daily variations in the temperature of the 1.58-μm emission. It is revealed that the behavior of these variations corresponds to daily variations in the atmospheric temperature at altitudes of the radiating layer of IRAO₂, received from the AURA satellite.     

Empirical model of variations in the emission of the infrared atmospheric system of molecular oxygen: 1. Intensity

On the basis of the data of ground-based spectrometric observations in Zvenigorod (55.7°N, 36.8°E) and published results of measurements of the intensity of the Infrared Atmospheric system of molecular oxygen obtained at other stations, empirical relations describing variations in the intensity of the 1.58-μm emission for various solar and geophysical conditions are calculated.     

Seasonal temperature variations near the mesopause according to the hydroxyl emission measurements in Zvenigorod

The rotational temperatures of hydroxyl molecules with different vibrational excitation, which were used to determine the seasonal variations in the vertical temperature distribution near the mesopause at altitudes of 85–90 km, have been obtained based on the spectral measurements of the atmospheric nightglow at IFA RAN observatory in Zvenigorod. The obtained characteristics of the annual and semiannual harmonics have been compared with their lidar and satellite measurements and model representations.     

Temperature variations in the mesopause region according to the hydroxyl-emission observations at midlatitudes

The seasonal temperature variations in the mesopause region and the inter-day and nighttime temperature variability, the measure of which is standard deviations, have been studied based on the hydroxyl emission spectral observations at the Zvenigorod station of the Obukhov Institute of Atmospheric Physics in 2000–2011 and Institute of Solar Terrestrial Physics geophysical station (Tory) in 2008–2011. The long-term variations in all temperature variability parameters have been analyzed.     

Ground-based observations of noctilucent clouds with a northern hemisphere network of automatic digital cameras

For the first time we present an analysis of observations of noctilucent clouds obtained with a network of automatic digital cameras located at opposite sides of the northern hemisphere. The advantage of this network is that the cameras are located along the same latitude circle producing comparable measurements. We find that there is an indication of the 2-day planetary wave propagation influencing the occurrence frequency, geographical distribution and brightness variations of noctilucent clouds. The 5-day planetary wave has much less effect on noctilucent clouds than that of the 2-day wave, at least for the summers of 2006 and 2007. At the same time, bright noctilucent clouds tend to occur every successive night during short periods of 3–5 nights.     

Seasonal and nighttime behaviors of emissions of hydroxyl and the atmospheric system of molecular oxygen of the midlatitude mesopause

Based on observations of mesopause emissions, namely, emissions of hydroxyl (band (6-2)) and molecular oxygen (band (0-1) of the atmospheric system), their systematic nighttime and seasonal variations are determined at Zvenigorod Observatory in 2000–2008. It is shown that the intensity of hydroxyl emission decreases during the entire night or first half-night, probably due to the influence of the chemical sink of atomic oxygen on the nighttime behavior of hydroxyl emission. The nighttime behavior of the intensity of molecular oxygen emission is explained by the action of atmospheric tides. The seasonal behavior of emissions is characterized by two minima, in April–May and December; it is caused by the annual behavior of the atomic oxygen content, temperature, and atmospheric density in the emitting layer. Based on the emission data, we determined the seasonal variations of atomic oxygen at heights of ∼87 km (maximum of hydroxyl emission) and ∼95 km (maximum of molecular oxygen emission).     

Spatial and temporal variations in infrared emissions of the upper atmosphere. 1. Atomic oxygen (λ 63 μm) emission

Rocket and balloon measurement data on atomic-oxygen (λ 63 µm) emission in the upper atmosphere are presented. The data from the longest (1989–2003) period of measurements of the atomic-oxygen (λ 63 µm) emission intensity obtained by spectral instruments on sounding balloons at an altitude of 38 km at midlatitudes have been systematized and analyzed. Regularities in diurnal and seasonal variations in the intensity of this emission, as well as in its relation with solar activity, have been revealed.     

Cryogenically cooled low-noise amplifier for radio-astronomical observations and centimeter-wave deep-space communications systems

We report a design solution for a highly reliable, low-noise and extremely efficient cryogenically cooled transmit/receive unit for a large antenna system meant for radio-astronomical observations and deep-space communications in the X band. We describe our design solution and the results of a series of laboratory and antenna tests carried out in order to investigate the properties of the cryogenically cooled low-noise amplifier developed. The transmit/receive unit designed for deep-space communications (Mars missions, radio observatories located at Lagrangian point L2, etc.) was used in practice for communication with live satellites including “Radioastron” observatory, which moves in a highly elliptical orbit.