Drift instabilities in anti-loss-cone plasmas

1976 ◽  
Vol 15 (1) ◽  
pp. 105-113 ◽  
Author(s):  
B. Buti
Keyword(s):  
Growth Rates ◽  
High Frequency ◽  
Low Frequency ◽  
Frequency Instability ◽  
Loss Cone ◽  
Electrostatic Waves ◽  
Low Frequency Instability ◽  
The Stability

The paper investigates the stability of electrostatic waves in non-uniform magnetoplasmas, governed by anti-loss-cone distributions. A new high- frequency anti-loss-cone instability occurs if ρ > ρc. (ρ is the parameter charactensing the strength of the anti-loss-cone.) An increase in ρ increases the growth rates for this instability, but stabilizes the low-frequency instability that exists even in the absence of the anti-loss cone. The growth rates can be of order 0.1Ωe.

Purely growing electromagnetic modes in high-β plasmas

1974 ◽  
Vol 11 (3) ◽  
pp. 461-470 ◽  
Author(s):  
G. S. Lakhina ◽  
B. Buti ◽  
Girija Nayar
Keyword(s):  
Magnetic Field ◽  
Growth Rates ◽  
Electromagnetic Waves ◽  
Low Frequency ◽  
Frequency Instability ◽  
Wave Number ◽  
Unstable Wave ◽  
Distribution Index ◽  
Kinetic Pressure ◽  
Low Frequency Instability

Electromagnetic waves propagating transverse to an external magnetic field in a high-β (β being the ratio of the kinetic pressure to the magnetic pressure) plasma become unstable through purely growing modes when β∥e, (electron β parallel to the magnetic field) exceeds a certain minimum value β∥*. For J ≦ 2 (J being the distribution index), the region of instability consists of a single band of unstable wavenumbers k, whereas for J ≥ 3 more than one unstable wave number band may exist. The growth rates are largest for J = 0, and tend to decrease as J increases. The presence of hot ions increases the instability region by exciting a low-frequency instability. This instability gets excited at considerably lowered values of β‖e, and has growth rates of the order of ion cyclotron frequency. The effect of T‖i/T‖e and T‖e/T⊥e is destabilizing, whereas that of T⊥i/T⊥e is stabilizing.

Secondary instability of cross-flow vortices in Falkner–Skan–Cooke boundary layers

1998 ◽  
Vol 368 ◽  
pp. 339-357 ◽  
Author(s):  
MARKUS HÖGBERG ◽  
DAN HENNINGSON
Keyword(s):  
Growth Rate ◽  
Shear Layer ◽  
Boundary Layers ◽  
Growth Rates ◽  
High Frequency ◽  
Cross Flow ◽  
Low Frequency ◽  
Secondary Instability ◽  
The Cross ◽  
Flow Vortex

Linear eigenvalue calculations and spatial direct numerical simulations (DNS) of disturbance growth in Falkner–Skan–Cooke (FSC) boundary layers have been performed. The growth rates of the small-amplitude disturbances obtained from the DNS calculations show differences compared to linear local theory, i.e. non-parallel effects are present. With higher amplitude initial disturbances in the DNS calculations, saturated cross-flow vortices are obtained. In these vortices strong shear layers appear. When a small random disturbance is added to a saturated cross-flow vortex, a low-frequency mode is found located at the bottom shear layer of the cross-flow vortex and a high-frequency secondary instability is found at the upper shear layer of the cross-flow vortex. The growth rates of the secondary instabilities are found from detailed analysis of simulations of single-frequency disturbances. The low-frequency disturbance is amplified throughout the domain, but with a lower growth rate than the high-frequency disturbance, which is amplified only once the cross-flow vortices have started to saturate. The high-frequency disturbance has a growth rate that is considerably higher than the growth rates for the primary instabilities, and it is conjectured that the onset of the high-frequency instability is well correlated with the start of transition.

scholarly journals Low-Frequency Instability Induced by Hopf Bifurcation in a Single-Phase Converter Connected to Non-Ideal Power Grid

IEEE Access ◽  
2020 ◽  
Vol 8 ◽  
pp. 62871-62882
Author(s):  
Hong Chen ◽  
Wenqian Yu ◽  
Zhigang Liu ◽  
Qixiang Yan ◽  
Ibrahim Adamu Tasiu ◽  
...  
Keyword(s):  
Hopf Bifurcation ◽  
Single Phase ◽  
Power Grid ◽  
Low Frequency ◽  
Frequency Instability ◽  
Phase Converter ◽  
Low Frequency Instability

scholarly journals Exploring the links between volcano flank collapse and the magmatic evolution of an ocean island volcano: Fogo, Cape Verde

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mélodie-Neige Cornu ◽  
Raphaël Paris ◽  
Régis Doucelance ◽  
Patrick Bachélery ◽  
Chantal Bosq ◽  
...  
Keyword(s):  
Large Scale ◽  
Low Frequency ◽  
Frequency Instability ◽  
Cape Verde ◽  
Magma Storage ◽  
Ocean Island ◽  
Flank Collapse ◽  
Time Space ◽  
Before And After ◽  
Low Frequency Instability

AbstractMass-wasting of ocean island volcanoes is a well-documented phenomenon. Massive flank collapses may imply tens to hundreds of km3 and generate mega-tsunamis. However, the causal links between this large-scale, low-frequency instability, and the time–space evolution of magma storage, crystal fractionation/accumulation, lithospheric assimilation, and partial melting remains unclear. This paper aims at tracking time variations and links between lithospheric, crustal and surface processes before and after a major flank collapse (Monte Amarelo collapse ca. 70 ka) of Fogo volcano, Cape Verde Islands, by analysing the chemical composition (major, trace elements, and Sr–Nd–Pb isotopes) and age-controlled stratigraphy (K–Ar and Ar–Ar dating) of lavas along vertical sections (Bordeira caldera walls). The high-resolution sampling allows detecting original variations of composition at different time-scales: (1) a 60 kyrs-long period of increase of magma differentiation before the collapse; (2) a 10 kyrs-long episode of reorganization of magma storage and evacuation of residual magmas (enriched in incompatible elements) after the collapse; and (3) a delayed impact at the lithospheric scale ~ 50 kyrs after the collapse (increasing EM1-like materiel assimilation).

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