Propagation of Stationary Planetary Waves in the Upper Atmosphere under Different Solar Activity

Numerical modeling of changes in the zonal circulation and amplitudes of stationary planetary waves are performed with an accounting for the impact of solar activity variations on the thermosphere. A thermospheric version of the Middle/Upper Atmosphere Model (MUAM) is used to calculate the circulation in the middle and upper atmosphere at altitudes up to 300 km from the Earth’s surface. Different values of the solar radio emission flux in the thermosphere are specified at a wavelength of 10.7 cm to take into account the solar activity variations. The ionospheric conductivities and their variations in latitude, longitude, and time are taken into account. The calculations are done for the January–February period and the conditions of low, medium, and high solar activity. It was shown that, during high-activity periods, the zonal wind velocities increases at altitudes exceeding 150 km and decreases in the lower layers. The amplitudes of planetary waves at high solar activity with respect to the altitude above 120 km or below 100 km, respectively, are smaller or larger than those at low activity. These differences correspond to the calculated changes in the refractive index of the atmosphere for stationary planetary waves and the Eliassen–Palm flux. Changes in the conditions for the propagation and reflection of stationary planetary waves in the thermosphere may influence the variations in their amplitudes and the atmospheric circulation, including the lower altitudes of the middle atmosphere.     

Numerical modeling of the propagation of nonlinear acoustic-gravity waves in the middle and upper atmosphere

A numerical algorithm for modeling the vertical propagation and breaking of nonlinear acoustic-gravity waves (AGWs) from the Earth’s surface to the upper atmosphere is described in brief. Monochromatic variations in the vertical velocity at the Earth’s surface are used as an AGW source in the model. The algorithm for solving atmospheric hydrodynamic equations is based on three-dimensional finite-difference analogues of fundamental conservation laws. This approach selects physically correct generalized solutions to hydrodynamic equations. A numerical simulation is carried out in an altitude region from the Earth’s surface to 500 km. Vertical profiles of the background temperature, density, and coefficients of molecular viscosity and heat conduction are taken from the standard atmosphere models. Calculations are made for different amplitudes of lower-boundary wave forcing. The AGW amplitudes increase with altitude, and waves may break in the middle and upper atmosphere.     

Results from field and stationary tests of the seismic signal recorder Delta 03

The operation of a new domestic seismic signal recorder Delta 03 is analyzed. The optimization of technical requirements on parameters of the recorder, the test cycle, adjustment in the process of testing individual technical solutions, and improvement of the device were carried out in close cooperation with its designers from OOO Logic Systems (Ramenskoye, Moscow Region). At the time of writing, the recorder Delta 03 is a robust device that is recommended for use in seismic monitoring systems of various levels.     

Comparison of the geoacoustic measurements in boreholes with the data of laboratory and in-situ experiments on electromagnetic excitation of rocks

The data of borehole geoacoustic and electromagnetic measurements in Kamchatka are compared with the results of laboratory and field experiments on electromagnetic excitation of rocks. A noticeable similarity in the responses of the natural geological medium and rock specimens is observed. The field experiments with controlled electromagnetic sources show that the geophones placed in boreholes are capable of reliably detecting the responses of rocks in situ to electric impacts as low as 0.5 mV/m. The obtained results provide the experimental evidence in favor of the previously proposed hypothesis of modulation of geoacoustic emission in rocks in situ by the ULF atmospheric electromagnetic field.     

Lithological and Geochemical Characteristics of the Paleocene/Eocene Sediments corresponding to the PETM Biospheric Event in the Eastern Crimea (Nasypnoe Section)

The paper reports lithological and geochemical data on the stratigraphic interval corresponding to the Paleocene/Eocene Thermal Maximum (PETM) event in the Paleogene section of Eastern Crimea (Nasypnoe section). The section is located on the western continuation of the sublatitudinal profile consisting of 15 PETM sections spanning the area from Crimea to Tajikistan (over 2500 km). It is shown that PETM sediments have the negative δ¹³C and δ¹⁸O isotope excursions and are enriched in kaolinite, which is typical of most sections of this interval around the world. At the same time, the extremely low content of organic matter (OM) in sediments of the Nasypnoe section makes them sharply different from the highly carbonaceous rocks of the PETM interval in Central and Eastern Caucasus, and Central Asian regions. This is correlated with the low contents of many chemical elements in the studied rocks, and their extremely high contents in the highly carbonaceous rocks of the easterly sections. Thus, Eastern Crimea in the end of the Paleocene?beginning of the Eocene was occupied by the low-bioproductive marine paleobasin, whereas the coeval paleobasin in Central Asia was characterized by extremely high bioproductivity owing to the presence of significant amount of phosphorus.     

Peculiarities of approximation of meteorological characteristics having vertical gradient discontinuities close to the tropopause

Carried out is an analysis of errors of different approximation methods for separating the long- and short-wave parts of the spectra of the vertical distribution of meteorological variables and gas components in the areas of dramatic variations of their vertical gradients close to the tropopause. Proposed is an integrated approach using the polynomial, piecewise-linear, and spectral filtration and enabling to minimize the errors of approximation of long- and short-wave components of profiles of meteorological characteristics in the troposphere and stratosphere including the tropopause area. The method is useful for analyzing the mean values and mesoscale variations of meteorological parameters measured by the modern balloon and satellite systems.     

Geochemistry of native gold from deposits of various types

The ICP-MS-analyzed 490 samples of lode and placer gold allowed us to detect a wide spectrum of trace elements in native gold from the most abundant gold-polysulfide-quartz, low-sulfide gold-quartz, and gold-silver deposits from various gold provinces and districts of the Russian Federation. The typical set of elements in gold of each deposit type has been determined. The distribution of REE, rare alkali and alkaline earth metals in native gold is estimated for the first time, and a geochemical index has been proposed to typify gold occurrences. Compositional differences of native gold are also caused by regional metallogenic features of gold provinces. The results obtained make it possible to determine a type of lode and placer gold occurrences at early stages of geological exploration.