Zonal Metamorphic Complex in the Tongulack Mountain Ridge, Altai, Russia, and Explanation of Its Origin with the Help of Thermal Modelling

A moderate pressure / high temperature zonal metamorphic complex in the Tongulack Mountain Ridge, Altai, Russia, is described, and the applicability of the models of magmatic intrusion and fluid flow to explanation of its origin discussed. The Precambrian complex was formed at 500-700℃ and 3.0-5.5 kbars; it is a linear, 25-30 km wide, thermal anticline with a curved axis showing symmetric metamorphic zoning. The metamorphism was isochemical by its nature, as is corroborated by the chemical compositions of the rocks. Four zones can be recognized within the metamorphic complex: chloritic (on the peripheries), cordieritic, sillimanitic and staurolite-out (in the centre). The zones are separated by successive isograds: cordierite, staurolite-in or sillimanite and staurolite-out. It is argued that the origin of the metamorphic zoning can be explained best by a combined fluid-magmatic model; conductive heat flow from the intrusion predominated considerably over the fluid flux in heat transfer: the fluid flow     

Ionospheric storm effects in the nighttime E region caused by neutralized ring current particles

During magnetic storms an anomalous increase in the ionization density of the nighttime E region is observed at low and middle latitudes. It has been suggested that this effect is caused by the precipitation of neutralized ring current particles. Here a coupled ring current decay-ionosphere model is used to confirm the validity of this explanation.     

Static spherical configurations of cold matter in the Einstein-Cartan theory of gravitation

We investigate static, spherical configurations of cold catalized matter in the Einstein-Cartan theory of gravitation. Assuming that density of spin is proportional to the number density of baryonsn and using an equation of state of a degenerate, relativistic Fermi gas, we numerically integrated the relativistic equation of equilibrium. We have also studied the stability of those configurations. Configurations with central number densityn _c such that where is the effective pressure, are very similar to general relativistic configurations with the same central density. In the Einstein-Cartan theory there exists another disjoint family of equilibrium configurations for which but . Those configurations have very small masses 10^–6 g and raddi 10^–34 cm and are unstable.Supported in part by Research Grant MR-I-7.     

Bending of fluid‐saturated linear poroelastic beams with compressible constituents

Analytical solutions are presented for fluid‐saturated linear poroelastic beams under pure bending. The stress‐free boundary condition at the lateral surfaces is satisfied in the St Venant's sense and the Beltrami–Michell compatibility conditions are resolved rigorously, rendering the flexure of the beams analytically tractable. Two sets of formulations are derived based on the coupled and uncoupled diffusion equations respectively. The analytical solutions are compared with three‐dimensional finite element simulations. Both sets of analytical formulations are capable of capturing exactly both the initial (undrained) and the steady‐state (fully drained) deflection of the beams. However, the analytical solutions are found to be deficient during the transient phase. The cause for the deficiency of the transient analytical solutions is discussed. The accuracy of the analytical solutions improves as Poisson's ratio and the compressibility of the constituents of the porous beam increase, where the St Venant's edge effect at the lateral surfaces is mitigated. Copyright © 2008 John Wiley & Sons, Ltd.     

Radiation production and energy deposition by ring current protons precipitated into the mid-latitude upper atmosphere

In the present paper the radiation production and energy deposition by ring current protons precipitated along magnetic field lines into the mid-latitude upper atmosphere is investigated. Specifically, we are interested in protons lost from the ring current by plasma instabilities. We first determine the magnitude and sharpness of the atmospheric loss cone. We then study the behavior of the precipitated hydrogen particles in the denser atmosphere using a Monte Carlo calculation. It is found that the energy deposition and radiation production will critically depend on how far the ring current protons diffuse into the loss cone before being neutralized in the atmosphere; this in turn will depend on the strength of the plasma turbulence in the ring current belt region.     

Decay of the magnetic storm ring current by the charge-exchange mechanism

Equatorial charge-exchange lifetimes of ring current protons are recalculated, and the decay of a collection of ring current protons trapped on an L-shell by the charge-exchange mechanism is determined using recent models of the hydrogen geocorona. Observational results pertaining to the decay of ring current energy are briefly discussed, as are a number of competing loss mechanisms. Since charge exchange is a simple physical process which is very efficient in removing ring current energy from L-shells near to the Earth (say, L < 4), it is suggested that it may well be the dominant loss mechanism in this region.     

Neutral composition changes during a period of increasing magnetic activity

Neutral composition data obtained by the gas analyzer aboard the satellite ESRO 4 are investigated for a period of increasing magnetic activity. The prominent feature observed is the development of localized disturbance zones in the high-and mid-latitude regions which show a significant enhancement in argon and nitrogen densities and a simultaneous decrease in helium densities. The behavior of oxygen within these zones is complex, and both increases and decreases are observed. Both the latitudinal extent and the magnitude of the disturbed regions increase with growing magnetic activity. In contrast the low-latitude region exhibits moderate enhancements of all constituents. Using the AE index as an indicator of magnetic activity, we find that at higher latitudes the atmospheric response time is of the order of one orbital revolution or less. Comparisons with other observations and with a theoretical model by Mayr and Volland (1974) show good agreement.     

On outlier-hiding effects in specific Gauss–Markov models: geodetic examples

 A specific subclass of Gauss–Markov models has been defined as containing the models for which the disturbance/response matrix, determined under the assumption of uncorrelated observations, consists of independent diagonal blocks. A proposed modification of reliability assessment procedure for such models is presented By the appropriate reduction of a given full covariance matrix for the observations, the proposal allows the assessment to be made in the resulting model which, in contrast to the initial model, is free from outlier-hiding effects of the type not occurring in ordinary models. The theoretical findings are demonstrated using simple numerical examples. All the proofs supporting the proposal are gathered in Appendixes. The proposal, which is not without its own weak points, is an attempt to associate the reliability assessment in specific Gauss–Markov models with effective outlier detection. Received: 23 June 1998 / Accepted: 5 July 2000     

Siliceous productivity changes in Gulf of Ancud sediments (42°S, 72°W), southern Chile,over the last ∼150 years

We evaluated changes in siliceous export production and the source of organic matter preserved in sediment core MD07-3109H recovered from the Gulf of Ancud, Chiloé Inner Sea (42°S, 72°W, water column depth: 328 m), southern Chile. We analyzed the abundance of siliceous microfossils (diatoms, silicoflagellates, sponge spicules, Chrysophyte cysts, phytoliths), geochemical proxies (weight percent silicon %Si_OPAL, organic carbon, total nitrogen, C/N molar), and sediment stable isotopes (δ¹³C_org, δ¹⁵N). Chronology based on ²¹⁰Pb and ¹⁴C provided an accumulated age of 144 years at the base of the core.Sediments of core MD07-3109H are predominantly marine in origin, averaging δ¹³C_org=–20.75‰±0.82, δ¹⁵N=8.7±0.35‰, and C/N=8.76±0.36. Marine diatoms compose 94% of the total assemblage of siliceous microfossils. Our record of productivity based on the mass accumulation rates of organic carbon, total nitrogen, Si_OPAL, and total diatoms showed high values between 1863 and 1869 AD followed by a declining trend until 1921 AD, a transition period from 1921 to 1959 AD with fluctuating values, and a clear decreasing pattern from 1960 AD to the present. This marked reduction in productivity was associated with decreased precipitation and Puelo River streamflow (41°S), as well as a warmer and more stratified water column, especially since the 1980s.     

A reactive transport simulator for variable porosity problems

ReactMiCP, a new reactive transport simulator was developed based on the semismooth speciation solver SpecMiCP. Its main feature is a sequential iterative operator splitting algorithm where macroscopic model parameters are explicitly included in the formulation. Its correctness, robustness, and efficiency are tested against the MoMaS benchmark and two sets of cement paste lab experiments. We show that a robust speciation solver is a key requirement for good performance of the reactive transport simulator. We also demonstrate that a sequential iterative solver should be preferred over non-iterative solvers when using operator splitting. The flexibility and the speed of the simulator are used to test the influence of the database, the initial condition, and the diffusion coefficient model for the cement paste simulations.