FESOM under coordinated ocean-ice reference experiment forcing

Characteristics of the ocean state simulated with the Finite-Element Sea-Ice Ocean Model (FESOM) under the normalized year forcing of Coordinated Ocean-ice Reference Experiments (COREs; Griffies et al., Ocean Model 26:1–46, 2009) are compared with those of other models participating in COREs. In contrast to these models, FESOM is run on an unstructured mesh (with resolution varying between 20 and 150 km). It is shown that the ocean state simulated by FESOM is in most cases within the spread of other models, demonstrating that the unstructured mesh technology has reached the stage when it becomes a reliable tool for studying the large-scale ocean general circulation.     

Variations in <Emphasis Type="Italic">foF</Emphasis>2 and <Emphasis Type="Italic">hmF</Emphasis>2 at the end of the 1990s and the beginning of the 2000s

This article considers sparse available data on variations in the main parameters of the ionospheric F2 layer foF2(ss + 2) and hmF2(ss + 2) at the end of the 1990s and the beginning of 2000s. It is shown that the monotonous behavior of hmF2(ss + 2) obtained in earlier publications for the period after 1980 is violated. The hmF2(ss + 2) behavior obtains a more complicated nature by time with a tendency towards a decrease in hmF2(ss + 2) at the beginning of a new century. A statistically significant relationship between foF2(ss + 2) and hmF2(ss + 2) is discovered confirming the Rishbeth statement that during the first hours after sunset, the critical frequency foF2 is governed by dynamical processes via changes in the F2-layer height. It is found that at the end of the interval in question, there is a tendency towards deviations from the above-mentioned dependence. The latter could be a manifestation of the fact that changes in the aeronomical parameters caused by the general cooling and contraction of the thermosphere begin influencing the foF2 value. It is found that in the summer months, the foF2(ss + 2) value demonstrated a systematic decline tendency from the “boundary date” towards the beginning of the 2000s.     

Critical frequencies <Emphasis Type="Italic">foF</Emphasis>2 as an indicator of trends in thermospheric dynamics

The time variations in three parameters during the last decades are considered. R(foF2) is the correlation coefficient between the nighttime and daytime values of foF2 for the same day. Stable trends are found for the minimum (R(foF2)(max)) and maximum (R(foF2)(min)) values of R(foF2) during a year. The foF2(night)/foF2(day) ratio demonstrates both, negative and positive trends, and the trend sign depends on the inclination I and declination D of the magnetic field. The correlation coefficient r(h, fo) between foF2 and the 100 hP level in the stratosphere demonstrates a decrease (in the years of maximum and minimum solar activity) from the 1980s to the 1990s. The trends in all three groups of data are considered under the assumption of long-term changes in the circulation in the upper atmosphere.     

Conditions and formation mechanism of carbon phases in late quarternary geyzerites and travertines of Ol’khon area and Ol’khon Island (Baikal rift zone)

Late Quaternary geyserite and travertine in Ol’khon Area and Ol’khon Island contain a recently discovered high-temperature association of hydrocarbon and carbonaceous phases, including highly crystalline graphite, α-carbyne, and bitumen, which were produced at temperatures no lower than 400°C. A carbon modification α-carbyne, which was previously found only among experimental products, was first identified in geyserite from the Ol’khon area. Nanometer-sized morphostructures and crystallites were detected on the surface of highly crystalline graphite from the geyserite and travertine. No such structures and crystallites have ever been found on graphite of magmatic, metamorphic, metasomatic, or pneumatolytic origin. The newly formed nanometer-sized morphostructures and crystallites should be regarded as typomorphic features of carbonaceous phases in high-temperature hydrothermal rocks. Graphite was likely produced in the geyserite and travertine by low-pressure polycondenssation of hydrocarbons, at free growth in open space from oversaturated solutions and/or a gas phase.     

Long-term trends in the ratio of the daytime and nighttime values of <Emphasis Type="Italic">foF</Emphasis>2

The consideration of the relation between the daytime and nighttime values of the critical frequency F2, foF2 of the ionospheric F2 layer, started in the previous publication of the authors, is continued. The main regularities in variations in the correlation coefficient R(foF2) characterizing this relation are confirmed using larger statistical material (more ionospheric stations and longer observational series). Long-term trends in the R(foF2) value are found: at all stations the negative value of R(foF2) increases with time after 1980.     

Phase-Density Fluctuations at the Centers of Six Open Clusters

Instability of proper fluctuations of the phase density at the centers of six open clusters is demonstrated. The boundaries of the region of instability in terms of the mean mass densities of the cluster cores are determined. Estimates for a number of dynamical parameters (the potential, velocity dispersion of the stellar motions, mass density, phase-density fluctuation period, time for the development of instability of the fluctuations, etc.) are obtained for the central parts of these clusters, as well as for numerical dynamical models for open clusters. Equation that can be used to estimate the dynamical mass of a cluster taking into account the influence of the external field of the Galaxy and the non-stationarity of the cluster is derived. Allowance for these effects makes it possible to decrease the dynamical masses of clusters compared to the virial masses assuming isolated systems. Astrophysical applications of the results are discussed.     

Dependence of magnetic activity on the plasma sheet location relative to the geomagnetic equator

Geomagnetic activity variations depending on the angle between the planes of geomagnetic equator and plasma sheet of the magnetosphere are considered on the basis of data of midlatitude stations. The dependences of diurnal variations proceeding in the universal time with opposite phases in winter and summer months, as well as the well-known semiannual variations in magnetic activity, on this angle are established. The amplitude of the diurnal wave displays substantial semiannual variations with maximums in the periods of solstices.