摘要:

The processes governing the propagation of low frequency vortex-wave convective disturbances in the two different physical systems of neutral fluids on rotating planets and plasmas confined by magnetic fields are explored with (i) physical descriptions of the convective transport, (ii) establishing the relevant conservation laws and (iii) computer simulations. The role of a global, ambient temperature gradient in driving the three-dimensional baroclinic instability is compared with the ion temperature gradient instability in magnetically confined plasma. Steady-state power balance and the turbulent viscosities and thermal diffusivities are analyzed using the same class of turbulent transport formulas. ©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.54441

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Most atmospheric and oceanic turbulence and eddies originate from the development of instabilities resulting from the combined effects of density gradients and rotation. We present here numerical Direct Numerical Simulations (DNS) and Large-Eddy Simulations (LES) of turbulent flows of atmospheric and oceanic interest. We first investigate the effects of solid-body rotation on free-shear flows, wall-bounded flows, and homogeneous turbulence, and show the drastic modification of the flow topology. Stably-stratified rotating turbulence is then numerically investigated with energy injection at small scales. We observe inverse cascades corresponding to a well definedk−5/3spectral range for the geostrophic part of both the kinetic and available potential energy spectra. The applications to the observed mesoscale atmospheric spectrum are discussed. We finally show how DNS and LES techniques can be applied to the computation of synoptic and frontal scale cyclogenesis. ©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.54436

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A review and the current status is given of laboratory experiments on the modeling, using rotating shallow water, of the largest and longest-lived vortical structures in planetary atmospheres, oceans, magnetized plasmas and spiral galaxies. Basic theoretical ideas, partly preceding the experiments mentioned and partly essentially inspired by the latter, are also presented. ©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.54442

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Basic vorticity principles give immediate insight into the behavior of turbulent flow of a classic, homogeneous fluid. Analogously, potential vorticity principles help to describe the large-scale flows of the Earth’s oceans and atmosphere, and those of the other planets; system rotation and density stratification are dominant effects. In both cases the tracer-like properties of vorticity and potential vorticity yield insight and analysis. The Ertel-Rossby potential vorticity arises essentially from Kelvin’s circulation theorem for fluid circuits lying on surfaces of constant potential density. Here we describe some of the dynamics of such fluids, notably the large-scale ‘geography’ of potential vorticity provided by the shape of the planet (or bounding container), waves that depend upon this geography, mean circulations that determine the geography, and geostrophic turbulence that actively help to shape this geography. The tracer-like property of potential vorticity encourages us to consider fluid circulations as being the product of boundary sources and sinks of potential vorticity, distributed by mean circulation and mixed (often homogenized) by geostrophic turbulence, with attendant back-effects on the mean circulation. ©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.54443

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The field of dusty plasmas is a new field that is rapidly developing and has many applications in laboratory, space and astrophysical contexts. The basic properties of dusty plasmas are reviewed and the effect of dust on drift waves and vortices is described. ©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.54438

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An overview for linear and nonlinear behavior of the resistive interchange mode and resistive drift wave is described. One specific point of view is interaction between resistive interchange turbulence and sheared flow induced by electric field in magnetically confined plasmas. Since the sheared flow produced by Reynolds stress suppresses the turbulent level, this mechanism may explain confinement improvement based on the L (Low mode) to H (High mode) transition and the ELMs (Edge Localized Modes) in tokamaks and stellarators. ©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.54439

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Theories for Jovian vortices are discussed from a historical perspective. Both weakly and strongly nonlinear approaches are reviewed. An observational indication of Jupiter’s Great Red Spot as a modon is noted. The historical observations suggest a catastrophic genesis of Jovian vortices, whose basic process appears to be understood by strongly nonlinear geostrophic adjustment. ©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.54440

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Self-organization and generation of a large shear flow component in turbulent resistive interchange convection in magnetized plasma is considered. The effect of plasma density-electrostatic potential coupling via the inertialess electron dynamics along the magnetic field is shown to play a significant role in the onset of the shear component. The results of large-scale numerical simulation and low-dimensional (reduced) model are presented and compared. ©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.54444

出版商:AIP    

年代:1997

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.54429

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We consider the heating of solar coronal active regions within a turbulent scenario. A direct numerical simulation of the equations governing the dynamics of a coronal magnetic loop is performed, assuming that the essential features can be described by an externally driven two-dimensional magnetohydrodynamic system. A stationary and large-scale magnetic forcing was imposed, to model the photospheric motions at the magnetic loop footpoints. A turbulent stationary regime is reached with an energy dissipation rate consistent with the heating requirements of coronal loops. The energy dissipation rate time series shows an intermittent behavior, in the form of impulsive events, superimposed on the stationary component. We associate the impulsive events of magnetic energy dissipation with the so-called nanoflares. A statistical analysis of these events yields a power law distribution as a function of their energies with a slope consistent with those obtained for flare energy distributions reported from X-ray observations. We also show the development of small scales in the spatial distribution of electric currents. ©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.54430

出版商:AIP    

年代:1997

数据来源: AIP