Instabilities of Jets and Fronts and their Nonlinear Evolution

2018 ◽  
Author(s):  
Vladimir Zeitlin
Keyword(s):  
Nonlinear Evolution ◽  
Baroclinic Instability ◽  
Trapped Modes ◽  
Nonlinear Saturation ◽  
Parallel Flows ◽  
Inertial Instability ◽  
Shear Instabilities ◽  
Linear And Nonlinear ◽  
Flow Configurations ◽  
Characteristic Features

Notions of linear and nonlinear hydrodynamic (in)stability are explained and criteria of instability of plane-parallel flows are presented. Instabilities of jets are investigated by direct pseudospectral collocation method in various flow configurations, starting from the classical barotropic and baroclinic instabilities. Characteristic features of instabilities are displayed, as well as typical patterns of their nonlinear saturation. It is shown that in the Phillips model of Chapter 5, new ageostrophic Rossby–Kelvin and shear instabilities appear at finite Rossby numbers. These instabilities are interpreted in terms of resonances among waves counter-propagating in the flow. It is demonstrated that the classical inertial instability is a specific case of ageostrophic baroclinic instability. At the equator it appears also in the barotropic configuration, and is related to resonances of Yanai waves. The nature of the inertial instability in terms of trapped modes is established. A variety of instabilities of density fronts is displayed.

Inertial versus baroclinic instability of the Bickley jet in continuously stratified rotating fluid

2014 ◽  
Vol 743 ◽  
pp. 1-31 ◽  
Author(s):  
Bruno Ribstein ◽  
Riwal Plougonven ◽  
Vladimir Zeitlin
Keyword(s):  
Gravity Waves ◽  
Large Scale ◽  
Large Range ◽  
Baroclinic Instability ◽  
Forecast Model ◽  
Rotating Fluid ◽  
Nonlinear Saturation ◽  
Unstable Region ◽  
Long Wave ◽  
Inertial Instability

AbstractThe paper contains a detailed study of the inertial instability of a barotropic Bickley jet on the $f$-plane in the continuously stratified primitive equations model, and a comparison of this essentially ageostrophic instability with the classical baroclinic one. Analytical and numerical investigation of the linear stability of the jet in the long-wave sector is performed for a range of Rossby and Burger numbers. The major results are that: (1) the standard symmetric inertial instability, appearing at high enough Rossby numbers, turns out to be the infinite-wavelength limit of an asymmetric inertial instability, this latter having the highest growth rate for a large range of vertical wavenumbers; (2) inertial instability coexists with the standard baroclinic instability, which becomes dominant at small Rossby numbers. Nonlinear saturation of the inertial instability of the jet with a superimposed random small-amplitude perturbation is then studied, using the Weather Research and Forecast model. It is shown that at first stages the inertial instability dominates. It is localized near the maximum of the anticyclonic shear and is associated with the highest attainable value of the vertical wavenumber. The saturation of the inertial instability leads to the homogenization of the geostrophic momentum in the unstable region. At later stages, another baroclinic instability develops, characterized by lower values of the vertical wavenumber. This instability saturates by forming large-scale vortices downstream. It is identified as the leading instability of a marginally inertially stable jet resulting from the initial one through homogenization of the geostrophic momentum. The rough scenario of the evolution of essentially ageostrophic jets is, thus, as follows: the inertial instability rapidly saturates and baroclinic instability takes over. It is shown that reorganization of the flow due to developing instabilities is an efficient source of inertia-gravity waves.

scholarly journals Linear and nonlinear optical responses in the chiral multifold semimetal RhSi

2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Zhuoliang Ni ◽  
B. Xu ◽  
M.-Á. Sánchez-Martínez ◽  
Y. Zhang ◽  
K. Manna ◽  
...  
Keyword(s):  
Nonlinear Optical ◽  
Chemical Potential ◽  
Technological Development ◽  
Optical Responses ◽  
Chiral Magnetic Effect ◽  
Hole Band ◽  
Linear And Nonlinear ◽  
Characteristic Features ◽  
Topological Semimetals ◽  
Terahertz Emission Spectroscopy

AbstractChiral topological semimetals are materials that break both inversion and mirror symmetries. They host interesting phenomena such as the quantized circular photogalvanic effect (CPGE) and the chiral magnetic effect. In this work, we report a comprehensive theoretical and experimental analysis of the linear and nonlinear optical responses of the chiral topological semimetal RhSi, which is known to host multifold fermions. We show that the characteristic features of the optical conductivity, which display two distinct quasi-linear regimes above and below 0.4 eV, can be linked to excitations of different kinds of multifold fermions. The characteristic features of the CPGE, which displays a sign change at 0.4 eV and a large non-quantized response peak of around 160 μA/V2 at 0.7 eV, are explained by assuming that the chemical potential crosses a flat hole band at the Brillouin zone center. Our theory predicts that, in order to observe a quantized CPGE in RhSi, it is necessary to increase the chemical potential as well as the quasiparticle lifetime. More broadly, our methodology, especially the development of the broadband terahertz emission spectroscopy, could be widely applied to study photogalvanic effects in noncentrosymmetric materials and in topological insulators in a contact-less way and accelerate the technological development of efficient infrared detectors based on topological semimetals.

Linear and nonlinear evolution of alpha-particle driven gap modes

1995 ◽  
Vol 37 (11A) ◽  
pp. A279-A290 ◽  
Author(s):  
S Briguglio ◽  
C Kar ◽  
F Romanelli ◽  
G Vlad ◽  
F Zonca
Keyword(s):  
Alpha Particle ◽  
Nonlinear Evolution ◽  
Linear And Nonlinear

scholarly journals Reconnection in Sheared Magnetic Fields in Space and Astrophysics

1985 ◽  
Vol 107 ◽  
pp. 61-81
Author(s):  
James F. Drake
Keyword(s):  
Energy Dissipation ◽  
Magnetic Fields ◽  
Nonlinear Evolution ◽  
Magnetic Energy ◽  
Coronal Loops ◽  
Theoretical Understanding ◽  
Physical Mechanisms ◽  
Linear And Nonlinear

The current theoretical understanding of the linear and nonlinear evolution of resistive tearing instabilities in sheared magnetic fields is reviewed. The physical mechanisms underlying this instability are emphasized. Some of the problems which are encountered in developing a model of magnetic energy dissipation in coronal loops are discussed and possible solutions are suggested.

Linear and nonlinear evolution of boundary layer instabilities generated by acoustic‐receptivity mechanisms

1996 ◽  
Vol 8 (6) ◽  
pp. 1415-1423 ◽  
Author(s):  
Kenneth S. Breuer ◽  
Elizabeth G. Dzenitis ◽  
Jonas Gunnarsson ◽  
Mats Ullmar
Keyword(s):  
Boundary Layer ◽  
Nonlinear Evolution ◽  
Linear And Nonlinear

scholarly journals Relativistic filamentary equilibria

2010 ◽  
Vol 77 (2) ◽  
pp. 193-205 ◽  
Author(s):  
M. GEDALIN ◽  
A. SPITKOVSKY ◽  
M. MEDVEDEV ◽  
M. BALIKHIN ◽  
V. KRASNOSELSKIKH ◽  
...  
Keyword(s):  
Current Sheet ◽  
Inertial Confinement Fusion ◽  
Nonlinear Evolution ◽  
Analytical Description ◽  
Inertial Confinement ◽  
Collisionless Shocks ◽  
Confinement Fusion ◽  
Linear And Nonlinear ◽  
Periodic Current

AbstractPlasma filamentation is often encountered in collisionless shocks and inertial confinement fusion. We develop a general analytical description of the two-dimensional relativistic filamentary equilibrium and derive the conditions for existence of potential-free equilibria. A pseudopotential equation for the vector-potential is constructed for cold and relativistic Maxwellian distributions. The role of counter-streaming is explained. We present single current sheet and periodic current sheet solutions, and analyze the equilibria with electric potential. These solutions can be used to study linear and nonlinear evolution of the relativistic filamentation instability.

Sign in / Sign up

Export Citation Format

Share Document