26 research outputs found
Correlation functions in isotropic and anisotropic turbulence: the role of the symmetry group
The theory of fully developed turbulence is usually considered in an
idealized homogeneous and isotropic state. Real turbulent flows exhibit the
effects of anisotropic forcing. The analysis of correlation functions and
structure functions in isotropic and anisotropic situations is facilitated and
made rational when performed in terms of the irreducible representations of the
relevant symmetry group which is the group of all rotations SO(3). In this
paper we firstly consider the needed general theory and explain why we expect
different (universal) scaling exponents in the different sectors of the
symmetry group. We exemplify the theory context of isotropic turbulence (for
third order tensorial structure functions) and in weakly anisotropic turbulence
(for the second order structure function). The utility of the resulting
expressions for the analysis of experimental data is demonstrated in the
context of high Reynolds number measurements of turbulence in the atmosphere.Comment: 35 pages, REVTEX, 1 figure, Phys. Rev. E, submitte
Relevance of Students' Civil Identity Formation: Major Trends and Challenges
В статье предпринята попытка подчеркнуть актуальность проблемы формирования гражданской идентичности и гражданской позиции среди студенческой молодежи. Рассматривается уровень исследования этой проблемы в научной литературе. На основе проведенного анализа уточняются определения «гражданская идентичность» и «гражданская позиция» в отношении студенческой молодежи. Выделяются противоречия, которые существуют в социально-педагогической практике, педагогической науке и деятельности преподавателей вузов на социально-педагогическом, научно-педагогическом и научно-методическом уровнях.This article attempts to emphasize the relevance of the problem of the formation of civic identity and civic position among students. The level of research of this problem in the scientific literature is considered. On the basis of the analysis, the definitions of "civil identity" and "civil position" in relation to student youth are specified. The contradictions that exist in socio-pedagogical practice, pedagogical science and the activities of university teachers at the socio-pedagogical, scientific-pedagogical and scientific-methodological levels are highlighted
Observation of inertial energy cascade in interplanetary space plasma
We show in this article direct evidence for the presence of an inertial
energy cascade, the most characteristic signature of hydromagnetic turbulence
(MHD), in the solar wind as observed by the Ulysses spacecraft. After a brief
rederivation of the equivalent of Yaglom's law for MHD turbulence, we show that
a linear relation is indeed observed for the scaling of mixed third order
structure functions involving Els\"asser variables. This experimental result,
confirming the prescription stemming from a theorem for MHD turbulence, firmly
establishes the turbulent character of low-frequency velocity and magnetic
field fluctuations in the solar wind plasma
On the Conductivity of a Magnetoactive Turbulent Plasma
The problem of determining the effective conductivity tensor of a
magnetoactive turbulent plasma is considered in the approximation of isolated
particles. Additional gyrotropicterms are shown to appear in the conductivity
tensor in the presence of mean, nonzero magnetic helicity. The dispersion of
propagating electro- magnetic waves changes, additional modes and additional
rotation of the polarization plane appear, and the waves can be amplified. The
properties acquired by plasma with helicity are similar those observed in
chiral and bianisotropic electrodynamic media.Comment: 15 page
Influence of helicity on scaling regimes in the extended Kraichnan model
We have investigated the advection of a passive scalar quantity by
incompressible helical turbulent flow in the frame of extended Kraichnan model.
Turbulent fluctuations of velocity field are assumed to have the Gaussian
statistics with zero mean and defined noise with finite time-correlation.
Actual calculations have been done up to two-loop approximation in the frame of
field-theoretic renormalization group approach. It turned out that space parity
violation (helicity) of turbulent environment does not affect anomalous scaling
which is peculiar attribute of corresponding model without helicity. However,
stability of asymptotic regimes, where anomalous scaling takes place, strongly
depends on the amount of helicity. Moreover, helicity gives rise to the
turbulent diffusivity, which has been calculated in one-loop approximation.Comment: 16 pages, talk given by M. Hnatich at "Renormalization Group 2005",
Helsinki, Finland 30 August - 3 September 2005. To apear in J. Phys. A: Math.
Ge
Antarctic polar vortex dynamics in 2019 and 2020 under the influence of the subtropical stratosphere
The trend of strengthening of the Antarctic polar vortex in late spring and early summer (November–December) has been observed in recent decades. A good example of this trend is the dynamics of the Antarctic polar vortex in 2020 when it existed until the last week of December. In 2019, conversely, on the contrary, an unusually early breakup of the polar vortex occurred, a minor sudden stratospheric warming was recorded. Strengthening (or weakening) of the Antarctic polar vortex occurs as a result of an increase (or decrease) in the stratospheric meridional temperature gradient under conditions of growth (or decline) in the temperature of the lower subtropical stratosphere. We considered the temperature variations in the lower subtropical stratosphere in the spring of 2019 and 2020 and the corresponding response of the Antarctic polar vortex. The dynamics of the Antarctic polar vortex in September–October 2019 and November 2020 was largely synchronized with the temperature changes in the lower subtropical stratosphere relative to climatological means. Using correlation analysis, we show that the Antarctic polar vortex dynamics in December is largely due to the temperature changes in the lower subtropical stratosphere that occurred in the second half of November, which manifested itself in 2020.The trend of strengthening of the Antarctic polar vortex in late spring and early summer (November–December) has been observed in recent decades. A good example of this trend is the dynamics of the Antarctic polar vortex in 2020 when it existed until the last week of December. In 2019, conversely, on the contrary, an unusually early breakup of the polar vortex occurred, a minor sudden stratospheric warming was recorded. Strengthening (or weakening) of the Antarctic polar vortex occurs as a result of an increase (or decrease) in the stratospheric meridional temperature gradient under conditions of growth (or decline) in the temperature of the lower subtropical stratosphere. We considered the temperature variations in the lower subtropical stratosphere in the spring of 2019 and 2020 and the corresponding response of the Antarctic polar vortex. The dynamics of the Antarctic polar vortex in September–October 2019 and November 2020 was largely synchronized with the temperature changes in the lower subtropical stratosphere relative to climatological means. Using correlation analysis, we show that the Antarctic polar vortex dynamics in December is largely due to the temperature changes in the lower subtropical stratosphere that occurred in the second half of November, which manifested itself in 2020