Electrodynamic heating and movement of the thermosphere

The theory of dissipation of ionospheric electric currents is extended to include viscosity. In a steady state (i.e. usually above about 140 km altitude) the joule plus viscous heating may be calculated by μ∇²v. E × B/B². At lower altitudes where viscosity may, in some circumstances, be relatively unimportant the joule dissipation is calculated by the usual formula j. (E + v × B). In a prevalent model of the auroral electrojets it is found that the joule heating can be much more intense outside auroral forms than within them. Heating due to auroral electrojets cause a semi-annual variation in the thermosphere. Movement caused by auroral electric fields make a contribution to the super-rotation of the midlatitude upper atmosphere. Random electric fields lead to an eddy ‘viscosity’ or ‘exchange coefficientrs in the upper thermosphere of magnitude ρE_R²/B³t_R²|∇E|. where t_R is the correlation time of the random component of electric fields E_R and ρ is air density. Theoretical conditions for significant heating by field-aligned currents are derived.     

Distances from auroral zones to the magnetic and geographic equators

Distance from auroral zone is a fundamental parameter in studies of disturbances produced in the thermosphere and ionosphere through the action of the solar wind. Calculations showing the great variation of the distances of the auroral “zones” from the magnetic equator and geographic equator are presented in diagrams. An auroral zone proximity index is proposed for use in correlative studies of upper atmosphere and of ionospheric disturbances.     

Effect of freeze—thaw cycles on resilient properties of fine-grained soils

Stress-deformation data for silt and clay subgrade soils were obtained from in-situ tests and laboratory tests, for use in mechanistic models for design of pavements that will experience freezing and thawing. Plate-bearing tests were run on in-service allbituminous-concrete (ABC) pavements constructed directly on silt subgrade, and on an experimental ABC pavement constructed on clay subgrade, applying repeated loads to the pavement surfaces while the subgrade was frozen, thawing, thawed, and fully recovered. The in-service pavement had experienced several seasons of natural cyclic freezing and thawing, while the experimental pavement was artificially frozen and thawed twice. Repeated-load laboratory triaxial compression tests were performed on the same soils in the frozen and thawed states.

Analysis of deflection data from the in-situ tests showed resilient moduli of the subgrade soils up to more than 10 GPa when frozen, as low as 2 MPa during the thawing period, and up to more than 100 MPa when fully recovered. Analysis of the laboratory tests, which gave moduli comparable to the latter values, showed that resilient modulus and Poisson's ratio in the thawed and recovering conditions can be expressed as a function of the stress state, the moisture content, and the dry density.     

Controls on the chemistry of springs at Teels Marsh,Mineral County,Nevada

Evaporative process plays a dominant role in determining the water chemistry of the springs at Teels Marsh, a closed basin in western Nevada. Analysis of the spring waters indicates that calcium, magnesium, sulfate, and silica are removed from solution during dry periods, even though groundwater is undersaturated with respect to gypsum, amorphous silica, and sepiolite. The removal mechanism is precipitation of authigenic phases such as gypsum above the water table, in the vadose zone.In episodes of rain and snowfall in which none of the waters enters the phreatic zone, ions in the rain and snow accumulate near the ground surface. This accumulation of material, together with the sparse rain and snowfall, inhibits chemical weathering of silicate minerals. Only at high elevations in the basin is there sufficient fluxing of water through the alluvium for silicate weathering to make a significant contribution to the sodium content of the springs. When a sufficiently heavy rainfall occurs, salts are partially dissolved and the ions transported to the permanent groundwater. The kinetics of dissolution of secondary phases in the vadose zone exert an important control on the composition of the springs.     

Internal differentiation and mantle composition of Mimas

An argument is given, based on considerations of moments of inertia and the equatorial location of the large crater Herschel, which implies that Mimas (one of the smallest satellites of the major planets) shows a high degree of internal differentiation (with a silicate-type core but a mantle with a density rather greater than for water-ice alone). Some consequences of these arguments are adduced and possible compositions of the mantle considered.     

Underwater camera system for deep‐sea bottom photography

A 35 mm camera system has been developed to operate to depths of 4,000 m. The system takes up to 24 pictures at one lowering, and uses standard torch batteries which last more than 10 lowerings.     

青海湖北岸土壤温度变化特征

利用1981-2008年刚察站0～320cm逐月平均土壤温度资料和2001-2008年逐日土壤温度观测资料,分析了青海湖北岸土壤温度变化特征、气候突变和异常年份.结果表明:各层年、季平均土壤温度呈现为极显著的升高趋势,升温率为0.25～0.91℃.(10a)-1;月平均土壤温度呈波形变化,位相随深度增加而滞后;日平均土壤温度呈正弦曲线变化;1月和10月随着深度的增加,土壤温度逐渐增大,4月和7月土壤温度随深度增加而减小;14:00时土壤温度随着深度增加逐渐下降,2:00时、8:00时和20:00时土壤温度随着深度增加而升高;除冬季5cm和15cm,秋季40cm平均土壤温度变化相对平稳,未出现突变现象外,其余各层年、季平均土壤温度均发生了突变;15cm、20cm、40cm、160cm和320cm年平均土壤温度均在20世纪80年代出现了异常偏冷,春季平均土壤温度出现了异常偏暖现象,其余各季和年平均地均表现为异常偏冷.