Long-lived center of youngest volcanism in the Borzhomi region of Georgia: Isotopic-geochronological evidence

Doklady Earth Sciences -     

Evaluation of summer temperature and precipitation forecasts generated by the MM5 model over central European Russia

The results of the MM5 regional meteorological model are compared with the station data. The simulations are carried out for the central part of the East European Plain for summer with a horizontal grid resolution of 15 km (24 × 34 grid points) and 24 vertical σ-levels, the upper level corresponding to 100 hPa. The MM5 model reliably reproduces information at a spatial scale of about 100 km, systematically overestimating temperature by about 1.5°C and underestimating daily precipitation totals by about 1 mm. The distribution functions for model and observed temperatures coincide with the Gaussian distribution function. The precipitation distribution functions are rather similar and have a form of the χ²-distribution with one degree of freedom. Station and model temperature extremes generally coincide in time. Extremes of daily precipitation totals are slightly underestimated by MM5.     

The beginning of volcanic activity within Sredinny metamorphic Massif (Sredinny Range,Kamchatka)

For the first time, the age of the beginning of the volcanic activity within Sredinny metamorphic Massif is determined (7–6 Ma). We suppose that this event was caused by the collision of Kamchatka with the Kronotsk arc that started about 7 Ma from accretion of Shipunsky peninsula. We demonstrate that at least two types of rocks were erupted within Sredinny Range of Kamchatka in late Miocene times: typical islandarc rocks were produced in the central and northern parts of the Range, and hybrid type rocks—in its southernmost part.     

Photodissociative absorption by H 2 + in the solar photosphere

Photoabsorption by systems of hydrogen atoms and protons in the solar photosphere is studied. Analytical formulas for the partial cross sections for photodissociation of the H ₂ ⁺ molecular ion are derived for the cases of fixed vibrational-rotational energy levels and averaging over a Boltzmann distribution for a given temperature. The photoabsorption coefficients for bound-free and free-free transitions of H-H⁺ in the solar photosphere are calculated. These are compared with the absorption coefficients for photo-ejection of an electron from a negative hydrogen ion H^? and free-free transitions of an electron in the field of a hydrogen atom H. Results can be applied to the Sun and hotter stars.     

Possibility of the discovery of eolian gold placers in Tuva

Issue of the influence of eolian processes on the formation of gold placers in the Tuva region is considered. It has been revealed that the formation of placers is related not only to hydrodynamic processes but also to eolian processes, which are reflected in the formation of relief, redistribution of metal, and reworking of the useful component. Study of typomorphic features of the eolian gold and regularities of its redistribution revealed the possibility of discovery of a new type of placer gold (eolian and heterogeneous placers).     

Laboratory simulation of energy release in solar flares

A laboratory simulation method is proposed for energy release processes occurring in a fragment of the flare current sheet on the Sun. The method relies on the assumption that the spatial scale of such processes is represented by the current sheet's thickness whose values can be close for both the solar and laboratory conditions. It is shown that in an extended current sheet, current dissipation on anomalous resistivity that ensures the specific power of energy release close to that observed in a flare, is the main energy release mechanism. A rapid compression of the sheet by external magnetic fields can provide the condition for switching on a powerful energy release. The tearing instability developing in a homogeneous neutral sheet, leads to the formation of magnetic islands in which the energy release is localized.