arXiv subjects

V. I. Ilgisonis

Publications and source records attributed to V. I. Ilgisonis.

4 recordsLinked to original sources

arXiv2015

Ion sound instability driven by ion beam

Ion sound instabilities driven by the ion flow in a system of a finite length are considered by analytical and numerical methods. The ion sound waves are modified by the presence of stationary ion flow resulting in negative and positive energy modes. The instability develops due to coupling of negative and positive energy modes mediated by reflections from the boundary. It is shown that the wave dispersion due to deviation from quasineutrality is crucial for the stability. In finite length system, the dispersion is characterized by the length of the system measured in units of the Debye length. The instability is studied analytically and the results are compared with direct, initial value numerical simulations.

physics.plasm-ph↗

arXiv2007

Energy of eigen-modes in magnetohydrodynamic flows of ideal fluids

Analytical expression for energy of eigen-modes in magnetohydrodynamic flows of ideal fluids is obtained. It is shown that the energy of unstable modes is zero, while the energy of stable oscillatory modes (waves) can assume both positive and negative values. Negative energy waves always correspond to non-symmetric eigen-modes -- modes that have a component of wave-vector along the equilibrium velocity. These results suggest that all non-symmetric instabilities in ideal MHD systems with flows are associated with coupling of positive and negative energy waves. As an example the energy of eigen-modes is calculated for incompressible conducting fluid rotating in axial magnetic field.

astro-ph↗

arXiv2007

Magnetorotational instability in electrically driven fluids

The linear stability of electrically driven flow of liquid metal in circular channel in the presence of vertical magnetic field is studied. It is shown that the instability threshold of such flow is determined by magnetorotational instability of non-axisymmetric modes ($m\neq0$) and does not depend on the type of the fluid if magnetic Prandtl number is small $\Pr\ll1$. Our numerical results are found to be in a good agreement with available experimental data from Grenoble High Magnetic Field Laboratory, France [P. Moresco and T. Alboussière, J. Fluid Mech. \textbf{504}, 167 (2004)].

astro-ph↗

arXiv2006

Magnetorotational Instability in Electrically Driven Flow of Liquid Metal: Spectral Analysis

The spectral stability of liquid metal differentially rotating in transverse magnetic field is studied numerically by solving the eigenvalue problem with rigid-wall boundary conditions. The equilibrium velocity profile used in calculations corresponds to the electrically driven flow in circular channel with the rotation law Ω(r)~1/r^2. This type of flow profile is planned to be used in new experimental device to test the magnetorotational instability (MRI) in laboratory. Our analysis includes calculations of the eigen-frequency spectra for both axisymmetric and non-axisymmetric modes. It is found that for chosen device parameters the flow is always spectrally unstable due to MRI with the fastest growth rate corresponding to the axisymmetric mode.

astro-ph↗