Basic Features of Global Circulation in the Mesopause Lower Thermosphere Region

D1 and D2 techniques have been used and are being used for observations at stations located in the high, middle, and low latitudes of both hemispheres. The systematical and wind velocity measurements with these techniques make it possible to specify and to refine earlier mesopause-lower thermosphere circulation models. With this in view, an effort was made to obtain global long term average height-latitude sections of the wind field at 70 to 110 km using the analysis of long period D1 and D2 observations. Data from 26 meteor radar and 6 ionospheric stations were taken for analysis

The climatic wind regime in the lower thermosphere from meteor radar observations

The determination of climatic norms of wind regime parameters in the lower thermosphere requires some questions of a methodical and scientific character to be settled. Among those of methodical character is: how to properly construct climatic circulation models using limited experimental data obtained by various methods during different time periods and in different geographical regions. The most important questions of a scientific character are: what main dynamic structures characterize the wind regime and how are these structures related to various atmospheric parameters and to the dynamic structures in the overlying and underlying atmospheric layers. These questions are considered and discussed

Ultra-depleted melts from Kamchatkan ophiolites : evidence for the interaction of the Hawaiian plume with an oceanic spreading center in the Cretaceous?

We report new data on the major and trace element composition of melt inclusions in spinel phenocrysts (Mg# = 0.7-0.8, Cr/(Cr + Al) = 0.32-0.52, TiO2 = 0.06-0.60 wt.%) from Cretaceous MORB-like basalt (La/Yb = 0.94, Th/Nb = 0.055, Th/La = 0.041) in the Kamchatsky Mys ophiolites (Eastern Kamchatka). The melt inclusions preserved primitive melts (Mg# up to 0.72), which are remarkably depleted in incompatible trace elements compared to common MORBs. Numerous ultra-depleted inclusions from the studied sample have extraordinarily low Na2O (0.20-0.67 wt.%), TiO2 (0.16-0.5 wt.%), K (1.5-25 ppm), La (0.015-0.040 ppm), Zr (0.9-2 ppm), B (0.01-0.03 ppm), Ti/Zr = 300-1074, La/Yb = 0.008-0.075 and represent the most depleted melts known until now. The ultra-depleted melts from the Kamchatkan ophiolites are only comparable to a single melt inclusion from MORB of 9 degrees N Mid-Atlantic Ridge [Sobolev and Shimizu, Nature 363 (1993) 151-154] yet have higher FeO, CaO, heavy rare-earth element (Dy, Er, Yb) contents and lower Na2O and SiO2. These melts, possibly the last melt fractions produced in an upwelling mantle column, could represent the highest degrees (up to similar to 20%) of near-fractional melting of mantle with T-p >= 1400 degrees C, which started melting at similar to 75 km depth and continued to shallow depths of similar to 20 km. The presence of melts ranging in composition from ultra-depleted to compositions similar to Mauna Loa Volcano, Hawaii, high potential mantle temperature and association with rocks akin the Cretaceous Hawaiian tholeiites suggest that the trace element depleted melts preserved in spinel phenocrysts could have originated from extensive melting of a depleted component intrinsic to the Hawaiian plume or ambient upper mantle entrained and heated up at the plume margins. (C) 2009 Elsevier B.V. All rights reserved

On the mechanism behind the fragmentation of tiny meteor bodies in the atmosphere

Fragmentation mechanism of small meteors during atmospheric entr

Large Scale Winter Time Disturbances in Meteor Winds over Central and Eastern Europe

Daily zonal wind data of the four pre-MAP-winters 1978/79 to 1981/82 obtained over Central Europe and Eastern Europe by the radar meteor method were studied. Available temperature and satellite radiance data of the middle and upper stratosphere were used for comparison, as well as wind data from Canada. The existence or nonexistence of coupling between the observed large scale zonal wind disturbances in the upper mesopause region (90 to 100 km) and corresponding events in the stratosphere are discussed

On the dependence of the lower thermospheric wind regime on the solar cycle

The lower thermosphere occupies the intermediate position between the overlying thermospheric layers, for which direct correlation of its parameters with solar variety variations is well established, and the underlying ones, where this correlation is mainly of an indirect character. Therefore, for understanding the mechanism of solar terrestrial correlation it is important to investigate the dependence of different atmospheric parameters in the lower troposphere, and of wind regime parameters in particular, on the solar activity. Several series of observations were used which include the results of meteor radar wind velocity measurements carried out in Obninsk complemented by the data obtained using the same technique at Jodrell Bank from 1953 to 1958 and in Kharkov from 1960 to 1963. The interannual variations of values averaged over these periods for prevailing wind velocities and semidiurnal harmonic amplitudes and also results for some months are presented. These results are discussed