scholarly journals Topological defects in crystals: A density-wave theory

1988 ◽  
Vol 10 (1-2) ◽  
pp. 45-51 ◽  
Author(s):  
M Raj Lakshmi ◽  
H R Krishna-Murthy ◽  
T V Ramakrishnan
Keyword(s):  
Density Wave ◽  
Topological Defects ◽  
Wave Theory ◽  
Defects In Crystals ◽  
Density Wave Theory

scholarly journals Fitting the Lin–Shu-type density-wave theory for our own Galaxy★

2013 ◽  
Vol 433 (3) ◽  
pp. 2511-2516 ◽  
Author(s):  
Evgeny Griv ◽  
Chow-Choong Ngeow ◽  
Ing-Guey Jiang
Keyword(s):  
Density Wave ◽  
Wave Theory ◽  
Density Wave Theory

scholarly journals Lifetime of density waves and classification of spirals

1979 ◽  
Vol 84 ◽  
pp. 155-156
Author(s):  
J. V. Feitzinger ◽  
Th. Schmidt-Kaler
Keyword(s):  
Density Wave ◽  
Wave Theory ◽  
Density Waves ◽  
Spiral Arms ◽  
Density Wave Theory

Checking the density-wave theory against observations of our own Galaxy has proven very difficult, as witnessed also at this Symposium. Less ambiguous results, however, are obtained for other galaxies. These results involve a) calculating convincing models for a sample of 25 fairly well observed spirals (Roberts et al. 1975) and b) locating the compression zones on the inner edges of the spiral arms.

scholarly journals On the use of the WKBJ density wave theory at the Inner Lindblad Resonance region of our galaxy

1979 ◽  
Vol 84 ◽  
pp. 191-192
Author(s):  
E. Athanassoula
Keyword(s):  
Density Wave ◽  
Wave Theory ◽  
Resonance Region ◽  
Density Wave Theory ◽  
Lindblad Resonance ◽  
Inner Lindblad Resonance

I have tested the reliability of certain approximations involved in the asymptotic WKBJ density wave description of the inner Lindblad resonance (=ILR) of our galaxy.

scholarly journals Galactic Dynamos and Density Wave Theory

1990 ◽  
Vol 140 ◽  
pp. 135-135
Author(s):  
L Mestel ◽  
K Subramanian
Keyword(s):  
Growth Rate ◽  
Angular Velocity ◽  
Numerical Solutions ◽  
Density Wave ◽  
Wave Theory ◽  
Interstellar Gas ◽  
Global Magnetic Field ◽  
Dynamo Equation ◽  
Density Wave Theory ◽  
Image Position

A steady density wave in the stellar background of a disk–like galaxy is supposed to force a spiral shock wave in the interstellar gas. The jump in vorticity across the shock leads to a locally enhanced helicity, and so to an α–effect which is steady but azimuth–dependent in the frame rotating with the angular velocity ω of the density wave. This is simulated by the adoption of the form for the local dynamo growth rate arising when the standard kinematic dynamo equation is treated by the thin–disk approximation (Ruzmaikin et al 1988). The global magnetic field is proportional to the function Q satisfying where η is the turbulent resistivity (for simplicity assumed uniform) and is the laminar angular velocity of the gas in the inertial frame. We look for solutions of the form where is a global eigen-value, and the non-vanishing of couples all odd or all the even m-values. Anticipating that the strong differential rotation will ensure that in the modes with the largest growth-rate the higher-m parts are weak, the equations are truncated, leaving just a pair in q1, q-1, to describe a basically bisymmetric (m = 1) mode. Approximate treatment by the WKBJ technique suggests that a corotating growing mode (with Γ real and positive) will differ significantly from zero over the range between the points where Numerical solutions have been found for a set of illustrative parameters with corotation occurring at 6.67 kpc, and the turbulence parameters close to those in the M51 mode studied by Ruzmaikin et al which extends over = 1 kpc. Three growing corotating modes were found, the fastest extending for ~ 3 kpc, the other two for over 4 kpc. The first two grow 2-3 times faster, the third somewhat slower, than the M51 mode.

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