scholarly journals A universal mirror wave-mode threshold condition for non-thermal space plasma environments

2002 ◽  
Vol 9 (2) ◽  
pp. 75-78 ◽  
Author(s):  
M. P. Leubner ◽  
N. Schupfer
Keyword(s):  
Wave Mode ◽  
Instability Threshold ◽  
Velocity Space ◽  
Space Distribution ◽  
Instability Criterion ◽  
Threshold Condition ◽  
Magnetic Fluctuations ◽  
Plasma Parameters ◽  
Energy Principle ◽  
Loss Cone

Abstract. Magnetic fluctuations are recognized in a large variety of space plasmas by increasingly high resolution, in situ observations as mirror wave mode structures. A typical requirement for the excitation of mirror modes is a dominant perpendicular pressure in a high-beta plasma environment. Contrary, we demonstrate from a realistic kinetic analysis how details of the velocity space distributions are of considerable significance for the instability threshold. Introducing the most common characteristics of observed ion and electron distributions by a mixed suprathermal-loss-cone, we derive a universal mirror instability criterion from an energy principle for collisionless plasmas. As a result, the transition from two temperature Maxwellians to realistic non-thermal features provides a strong source for the generation of mirror wave mode activity, reducing drastically the instability threshold. In particular, a number of space-related examples illuminate how the specific structure of the velocity space distribution dominates as a regulating excitation mechanism over the effects related to changes in the plasma parameters.

scholarly journals Mirror structures above and below the linear instability threshold: Cluster observations, fluid model and hybrid simulations

2009 ◽  
Vol 27 (2) ◽  
pp. 601-615 ◽  
Author(s):  
V. Génot ◽  
E. Budnik ◽  
P. Hellinger ◽  
T. Passot ◽  
G. Belmont ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Fluid Model ◽  
Linear Instability ◽  
Instability Threshold ◽  
Magnetic Fluctuations ◽  
Plasma Parameters ◽  
Cluster Data ◽  
Detailed Statistical Analysis ◽  
Formation And Evolution ◽  
Stable Plasma

Abstract. Using 5 years of Cluster data, we present a detailed statistical analysis of magnetic fluctuations associated with mirror structures in the magnetosheath. We especially focus on the shape of these fluctuations which, in addition to quasi-sinusoidal forms, also display deep holes and high peaks. The occurrence frequency and the most probable location of the various types of structures is discussed, together with their relation to local plasma parameters. While these properties have previously been correlated to the β of the plasma, we emphasize here the influence of the distance to the linear mirror instability threshold. This enables us to interpret the observations of mirror structures in a stable plasma in terms of bistability and subcritical bifurcation. The data analysis is supplemented by the prediction of a quasi-static anisotropic MHD model and hybrid numerical simulations in an expanding box aimed at mimicking the magnetosheath plasma. This leads us to suggest a scenario for the formation and evolution of mirror structures.

Electromagnetic ion-cyclotron instability vs. electrostatic ion-cyclotron instability in mixed (warm-cold) magnetospheric-like plasmas

1977 ◽  
Vol 18 (3) ◽  
pp. 391-413 ◽  
Author(s):  
S. Cuperman ◽  
L. Gomberoff
Keyword(s):  
Electromagnetic Coupling ◽  
Maximum Growth ◽  
Systematic Investigation ◽  
Maximum Growth Rate ◽  
Plasma Parameters ◽  
Loss Cone ◽  
Cyclotron Instability ◽  
Ion Cyclotron ◽  
Validity Range ◽  
Approximate Expressions

This work presents a systematic investigation and comparison of electromagnetic ion-cyclotron (e.m.) and electrostatic ion-cyclotron (e.s.) instabilities in uniform mixed warm and cold plasmas for magnetospheric-like plasma parameters. The following main aspects are included: Analytical: (i) we derive simple approximate expressions for the maximum growth rate, γmax for the quasi-electrostatic instability in the regime ωr » …p, к┴ » к∥ (к∥ ≠ 0) with the protons being described by mixed loss-cone and cold populations and with inclusion of electromagnetic coupling effects due to electrons; (ii) we analyse another regime in which electrostatic instalilities first increase with addition of cold plasma and decrease only after having reached a maximum, namely a regime with ωr » …p, к = к≠; (iii) we summarize the corresponding analytical results for parallel propagating electromagnetic ion-cyclotron unstable waves and discuss their validity range.

Ion acoustic waves in expanding strongly coupled plasmas

2013 ◽  
Vol 79 (6) ◽  
pp. 1063-1066 ◽  
Author(s):  
J. T. MENDONÇA ◽  
N. SHUKLA ◽  
D. P. RESENDES ◽  
A. SERBETO
Keyword(s):  
Acoustic Waves ◽  
Temporal Change ◽  
Wave Mode ◽  
Mode Structure ◽  
Plasma Parameters ◽  
Ion Acoustic Waves ◽  
Strongly Coupled ◽  
Ultracold Plasmas ◽  
Ion Acoustic ◽  
Coupled Plasmas

AbstractWe consider the excitation and dispersion of ion acoustic waves in expanding ultracold plasmas, taking into account the influence of boundary conditions. A cylindrical plasma geometry is assumed. We show that temporal changes in the medium lead to a wave frequency shift, associated with an evolving radial and standing wave mode structure, and to the temporal change of the background plasma parameters. A non-collisional model for the cylindrical geometry is also proposed.

Threshold condition for spray formation by Faraday instability

2014 ◽  
Vol 759 ◽  
pp. 73-103 ◽  
Author(s):  
Yikai Li ◽  
Akira Umemura
Keyword(s):  
Surface Wave ◽  
Liquid Layer ◽  
Initial Conditions ◽  
Inertial Force ◽  
Wave Mode ◽  
Experimental Investigations ◽  
Threshold Condition ◽  
Liquid Density ◽  
Spray Formation ◽  
Faraday Instability

AbstractA vertically vibrating liquid layer produces liquid ligaments that disintegrate to form a spray with drops of a controllable size. Previous experimental investigations of ultrasonic atomisation have shown that when such a spray forms, there exists a predominant surface-wave mode from which drops are generated with a mean diameter that follows Lang’s equation. In this paper, we determined this predominant surface-wave mode physically and, by utilising the coupled level-set and volume-of-fluid method, we numerically studied the threshold condition for spray formation based on a cell model of the predominant surface wavelength that excludes the effects of the container walls. We defined a condition whereby the broken drop holds a zero area-averaged vertical velocity in the laboratory reference frame as the criterion for the formation of a spray. The results of our calculations indicated that the onset of a spray occurs in the subharmonic unstable region for a threshold dimensionless forcing strength ${\it\beta}_{c}=({\it\rho}_{l}{\it\Delta}_{0}^{3}{\it\Omega}^{2})/{\it\sigma}\sim O(1)$, where ${\it\rho}_{l}$ and ${\it\sigma}$ denote the liquid density and surface tension coefficient, respectively, ${\it\Delta}_{0}$ is the forcing displacement amplitude and ${\it\Omega}$ is the forcing angular frequency. Spray formation due to the Faraday instability can be considered as a process whereby the liquid layer absorbs energy from the inertial force, and releases it by producing drops that leave the surface of the liquid layer. We demonstrated that for a deep liquid layer, the threshold condition for the formation of a spray is determined only by the forcing strength, and is independent of the initial conditions of the liquid surface.

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