Undamped Oscillations of Electric Current in Coronal Magnetic Loops and in Magnetic Loop Arcades

Geomagnetism and Aeronomy - The possibility of the existence of undamped oscillations of the electric current in coronal magnetic loops and loop arcades due to the presence of a photospheric...     

Evolution of Electric Current and Resistance in the Flare Loop in the Course of Loop Shrinkage

Geomagnetism and Aeronomy - Analysis of the phenomenon of the shrinkage of a coronal magnetic loop during the impulsive phase of a flare makes it possible to determine both the evolution of...     

Gyrosynchrotron Model of Microwave Sources Associated with the Magnetic Field Neutral Line

Geomagnetism and Aeronomy - The main properties of microwave radiation sources over the magnetic field neutral line, which follow from the assumption of a gyrosynchrotron mechanism of radio...     

Strong Tidal Mixing and Ventilation of Cold Intermediate Water at Kashevarov Bank, Sea of Okhotsk

Tidal mixing at the Kashevarov Bank, Sea of Okhotsk, has been investigated using observations of bottom pressure and currents. The tides are dominated by the diurnal constituents. The water motion over the Bank is predominantly controlled by strong diurnal tidal currents, which bring cold water on the bank from its source, a cold intermediate layer. The temperature fluctuations are about 1.2°C at the southern edge of the bank. The maximum observed velocity is about 164 cm/s at the top of the bank. A superposition of the original diurnal constituents K₁ and O₁ reveals a strong fortnightly (M_f) variability of the current speed. Tidal-induced mixing is responsible for ventilation of the cold intermediate layer of the Sea of Okhotsk. Strong tidal mixing creates a well-defined tidally mixed front around the bank. This front acts like a barrier separating well-mixed water on the bank from stratified water on its flanks. There is a residual current of the order of 10 cm/s.     

Influence of the Solar Activity Cycle on the Gasdynamic Structureof the Heliospheric Interface

The effects of the 11 year solar activity cycle on the heliospheric plasma interface in the presence of neutral H-atoms have been investigated. Our calculations show that nonstationary processes of such kind lead to1) a decrease of the mean interstellar plasma density in the interface;2) a sequence of shocks and rarefaction waves moving from the heliopause (HP)to the bow shock (BS); 3) an expansion of the region between the BS and HP;4) the TS excursion along the upwind direction is within 30%of the mean solar distance. This revised version was published online in July 2006 with corrections to the Cover Date.     

Acceleration and Storage of Energetic Electrons in Magnetic Loops in the Course of Electric Current Oscillations

A mechanism of electron acceleration and storage of energetic particles in solar and stellar coronal magnetic loops, based on oscillations of the electric current, is considered. The magnetic loop is presented as an electric circuit with the electric current generated by convective motions in the photosphere. Eigenoscillations of the electric current in a loop induce an electric field directed along the loop axis. It is shown that the sudden reductions that occur in the course of type IV continuum and pulsating type III observed in various frequency bands (25?–?180 MHz, 110?–?600 MHz, 0.7?–?3.0 GHz) in solar flares provide evidence for acceleration and storage of the energetic electrons in coronal magnetic loops. We estimate the energization rate and the energy of accelerated electrons and present examples of the storage of energetic electrons in loops in the course of flares on the Sun or on ultracool stars. We also discuss the efficiency of the suggested mechanism as compared with the electron acceleration during the five-minute photospheric oscillations and with the acceleration driven by the magnetic Rayleigh–Taylor instability.     

Seasonal Cycle of the Near-Surface Diurnal Wind Field Over the Bay of La Paz,Mexico

The results of numerical simulations of the troposphere over the Bay of La Paz, calculated for the months of January, April, July and October during the period 2006–2010 with the Weather Research and Forecast (WRF v3.5) regional model, are used to describe the seasonal features of the diurnal cycle of planetary boundary-layer winds. Two distinct near-surface diurnal flows with strong seasonal variability were identified: (1) a nocturnal and matutinal breeze directed from the subtropical Pacific Ocean, over the Baja California peninsula and the Bay of La Paz, into the Gulf of California that is associated with the regional sea-surface temperature difference between those two major water bodies; and (2) a mid to late afternoon onshore sea-breeze related to the peninsula’s daily cycle of insolation heating that evolves with counter-clockwise rotation over the Bay of La Paz. The model results reveal the interaction over Baja California of opposing afternoon sea-breeze fronts that originate from the subtropical Pacific Ocean and the Gulf of California, with a convergence line forming over the peaks of the peninsula’s topography and the associated presence of a closed vertical circulation cell over the Bay of La Paz and the adjacent Gulf. The collision of the opposing sea-breeze fronts over the narrow peninsula drives convection that is relatively weak due to the reduced heat source and only appears to produce precipitation sporadically. The spatial structure of the sea-breeze fronts over the Bay of La Paz region is complex due to shoreline curvature and nearby topographic features. A comparison of the numerical results with available meteorological near-surface observations indicates that the modelling methodology adequately reproduced the observed features of the seasonal variability of the local planetary boundary-layer diurnal wind cycle and confirms that the low-level atmospheric circulation over the Bay of La Paz is dominated by kinetic energy in the diurnal band. The strongest (weakest) diurnal flows occur during the summer (winter) in response to the seasonally varying magnitudes of the daily land–sea thermal contrast and the regional subtropical Pacific Ocean–Gulf of California sea-surface temperature difference.     

Kimberlites of the Manchary pipe: a new kimberlite field in Central Yakutia

This paper reports new petrographic and mineralogical data on the Manchary kimberlite pipe, which was discovered south of Yakutsk (Central Yakutia) in 2007–2008, 100 km. The pipe breaks through the Upper Cambrian carbonate deposits and is overlain by Jurassic terrigenous rock masses about 100 m thick. It is composed of greenish-gray kimberlite breccia with a serpentine-micaceous cement of massive structure. The porphyry texture of kimberlite is due to the presence of olivine, phlogopite, and picroilmenite phenocrysts. The SiO₂ and Al₂O₃ contents of the groundmass are indicative of typical noncontaminated kimberlites. The groundmass has a significant content of ore minerals: Fe- and Cr-spinels, perovskite, magnetite, and, less commonly, magnesian Cr-magnetite. Pyropes occur in kimberlites as sharp-edged fragments and show uneven distribution. Chemically, they belong to lherzolite, wehrlite, or nondiamondiferous dunite–harzburgite parageneses. Garnets corresponding to lherzolites of anomalous composition make up 8%; this is close to the garnet content of Middle Paleozoic kimberlites from the Yakutian kimberlite province. The pyropes from the new pipe are compositionally similar to those from diamond-poor Middle Paleozoic kimberlites in the north of the Yakutian diamondiferous province. Chemically, pyropes from the Manchary pipe and those from the modern alluvium of the Kengkeme and Chakyya Rivers differ substantially. Consequently, the rocks of the pipe could not be a source of pyropes for this alluvium. They probably occured from other sources. This fact along with numerous “pipelike” geophysical anomalies, suggest the existence of a new kimberlite field in Central Yakutia.     

The tsunami on Sakhalin on August 2, 2007: Mareograph evidence and numerical simulation

Instrumental data on the tsunami registration on Sakhalin and Hokkaido islands are presented. The numerical simulation of the tsunami propagation in the Tatar Strait was performed. The results of the calculations are in satisfactory agreement with the observed data.     

Community Structure in the Amber Forest: Study of the Arthropod Syninclusia in the Rovno Amber(Late Eocene of Ukraine)

<正>Arthropodan syninclusions in the Late Eocene Rovno amber were examined using x~2 to reveal correlation of the component groups(some taxa of Diptera,ants,aphids,and mites) supposedly indicative of the biocoenotic relationships in the ancient amber forest.Three tightly correlated groups were identified,representing a putative aerial plankton guild(Chironomidae+Ceratopogonidae) and two tree-trunk guilds,one of which (Dolichopodidae+Germaraphis) is possibly connected to more open or/and more hygrophilous habitats than the other(Sciara zone Diptera +"Acarus"rhombeus).The ants were not linked with any of the above components.