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.

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.

Experimental Investigation of a Low Frequency Instability in a Modified Penning Discharge (Q-PIG)

1970 ◽  
Vol 25 (2) ◽  
pp. 263-273
Author(s):  
F . Klan
Keyword(s):  
Magnetic Field ◽  
Experimental Investigation ◽  
Electron Gas ◽  
Low Frequency ◽  
Frequency Instability ◽  
Qualitative Explanation ◽  
Low Frequency Oscillations ◽  
Low Frequency Instability ◽  
Low Magnetic Field ◽  
Detailed Picture

Abstract Low frequency oscillations observed in a modified PIG discharge were identified as fluctuations of the electron temperature. These oscillations only occurred under certain conditions (low gas pressure, relatively high magnetic field), whereas at high pressure and low magnetic field strength the plasma was remarkably stable; this is why the discharge is referred to as a "quiescent" PIG (Q-PIG) discharge. This paper describes measurements for obtaining a detailed picture of the two modes of the discharge. A qualitative explanation of the phenomena observed is obtained using the energy balance of the electron gas.

Finite Beta Drift Cyclotron Instabilities in an Inhomogeneous Plasma

1974 ◽  
Vol 52 (14) ◽  
pp. 1265-1273 ◽  
Author(s):  
Yoshihiro Higuchi
Keyword(s):  
Magnetic Field ◽  
Growth Rates ◽  
Magnetic Field Gradient ◽  
Inhomogeneous Plasma ◽  
Maximum Growth ◽  
Resonant Mode ◽  
Wave Number ◽  
Resonant Modes ◽  
Instability Growth ◽  
Kinetic Pressure

The effect of finite beta (the ratio of plasma kinetic pressure to magnetic field pressure) on drift cyclotron instabilities for the nonresonant and ion resonant modes are investigated through numerical analysis of their dispersion relations. For the nonresonant mode, it is found that the two unstable regions are merged into one unstable region, if the steep density gradient is decreased, and there is a new mode which has approximately ion cyclotron frequency due to the effect of finite beta. For ion resonant convective modes (kz ≠ 0), finite beta greatly reduces the instability growth rates, though it does not remove instabilities completely. Furthermore, the effects of magnetic field gradient and curvature are examined. It is found for the nonresonant mode that the maximum growth rates are slightly enhanced. For the ion resonant mode, they are slightly reduced and the wave number of the fastest growing wave is increased as the gradient and curvature drift velocity are decreased.

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).

Low-frequency instability in semi-insulator GaAs

1966 ◽  
Vol 54 (6) ◽  
pp. 890-891 ◽  
Author(s):  
J. Bohm ◽  
G.W. Farnell
Keyword(s):  
Low Frequency ◽  
Frequency Instability ◽  
Low Frequency Instability
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