2In weakly collisional space plasmas, the turbulent cascade provides most of the energy that is dissipated at small scales by various kinetic processes. Understanding the characteristics of such dissipative mechanisms requires the accurate knowledge of the fluctuations that make energy available for conversion at small scales, as different dissipation processes are triggered by fluctuations of a different nature. The scaling properties of different energy channels are estimated here using a proxy of the local energy transfer, based on the third-order moment scaling law for magnetohydrodynamic turbulence. In particular, the sign-singularity analysis was used to explore the scaling properties of the alternating positive-negative energy fluxes, thus providing information on the structure and topology of such fluxes for each of the different type of fluctuations. The results show the highly complex geometrical nature of the flux, and that the local contributions associated with energy and cross-helicity nonlinear transfer have similar scaling properties. Consequently, the fractal properties of current and vorticity structures are similar to those of the Alfvénic fluctuations. PACS numbers: 94.05.-a, 94.05.Lk, 95.30.Qd
Abstract. Some results of simulation of the Black Sea circulation with consideration of forcing of different averaged wind types by using 3-D prognostic baroclinic model are presented. The results allow us to consider all depth of the sea basin consisting of some relatively homogeneous sub-layers. Within each of them general circulation processes practically do not change by depth, but essentially change from layer to layer. Such character of changeability interpreted by us as a steepness of the Black Sea general circulation takes place in majority cases of climatic atmospheric wind forcing. In the present paper results are analyzed on an example of forcing of January atmospheric cyclonic vortex with ~250 km diameter. Under such forcing the Ekman surface layer of ~12 m thickness is created. The cyclonic vortex formed in the east part of the Black Sea, which is Taylor-Proudman potential vortex with vertical cylindrical configuration, is described in detail. The vertical distribution of vortex characteristics are given in figures: Brunt-Väisälä frequency and Richardson number taken near the vortex wall with maximal velocity. The viable vortexes are characterized by introduced the universal Reynolds number Re•.
The terrestrial magnetosheath is characterized by large-amplitude magnetic field fluctuations. In some regions, and depending on the bow-shock geometry, these can be observed on several scales, and show the typical signatures of magnetohydrodynamic turbulence. Using Cluster data, magnetic field spectra and flatness are observed in two intervals separated by a sharp transition from quasi-parallel to quasi-perpendicular magnetic field with respect to the bow-shock normal. The multifractal generalized dimensions Dq and the corresponding multifractal spectrum f(α) were estimated using a coarse-graining method. A p-model fit was used to obtain a single parameter to describe quantitatively the strength of multifractality and intermittency. Results show a clear transition and sharp differences in the intermittency properties for the two regions, with the quasi-parallel turbulence being more intermittent.
The study of water circulation and thermohaline processes in the coastal zones of the seas and oceans, subjected to the most intense anthropogenic press, is an important problem of modern Oceanology. According to experimental and theoretical researches the coastal water areas of the Black Sea are dynamically active regions, where intensive generation of mesoscale and submesoscale eddies takes place. Such eddies make a significant contribution to the horizontal and vertical transport of different polluting substances, heat, momentum, etc. Therefore, the modeling and study of main peculiarities of variability of regional dynamic processes is of great scientific and practical interest. The goal of this study is to investigate numerically the structure and spatial –temporal distribution of the sea flow and thermohaline fields taking place during the period 2017-2019 in the easternmost part of the Black Sea, which is limited from the open part of the sea basin with liquid boundary coinciding 39.080E. With this purpose a high-resolution numerical regional model of the Black Sea dynamics of M. Nodia Institute of Geophysics of I. Javakhishvili Tbilisi State University (RM-IG) is used. The RM-IG is nested in the basin-scale model of the Black Sea dynamics of Marine Hydrophysical Institute (Sevastopol) and is based on a primitive system of ocean hydrothermodynamics equations. The RM-IG uses a calculated grid having 215x347 points on horizons with 1 km spatial resolution. Results of researches presented in the paper show significant variability of the regional dynamic processes in the easternmost water area during 2017-2019, where continuously generation, deformation and disappearance of the cyclonic and anticyclonic vortex formations of difference sizes takes plac
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