MHD instabilities of a cylindrical plasma with a realistic energy equation

1987 ◽  
Vol 37 (2) ◽  
pp. 175-184 ◽  
Author(s):  
Guidetta Torricelli-Ciamponi ◽  
Vittorio Ciampolini ◽  
Claudio Chiuderi
Keyword(s):  
Magnetic Field ◽  
Time Scales ◽  
Growth Rates ◽  
Thermal Conduction ◽  
Energy Equation ◽  
Magnetized Plasma ◽  
Line Radiation ◽  
Mhd Instabilities ◽  
Solar Plasmas ◽  
The Stability

The influence of a realistic energy equation on the stability of a cylindrical magnetized plasma in a force-free magnetic field is discussed. Thermal conduction, heating and line radiation are included in the treatment. Explicit growth rates for the m = 0 and m = 1 modes are derived and compared with the standard adiabatic or incompressible time-scales. Finally, the relevance of these results for laboratory and solar plasmas is discussed.

Theory of Raman sidescatter from a magnetized plasma

1984 ◽  
Vol 32 (2) ◽  
pp. 331-346 ◽  
Author(s):  
H. C. Barr ◽  
T. J. M. Boyd ◽  
R. Rankin
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Wave ◽  
Growth Rates ◽  
Scattered Light ◽  
Critical Density ◽  
Magnetized Plasma ◽  
Frequency Shifts ◽  
Wave Growth ◽  
Circularly Polarized ◽  
The Magnetic Field

The effects of a d.c. magnetic field on stimulated Raman sidescatter from laser-produced plasmas is studied. For exact sidescatter along the magnetic field, the Raman instability separates into two distinct decays in which the scattered light is either a right (RHCP) or left (LHCP) circularly polarized electromagnetic wave. Growth rates of the instabilities can be enhanced in the former case but are diminished in the latter. The magnetic field induced effects are greatest near the quarter critical density where frequency shifts can be especially significant, being equal to ± ¼Ωc for decay into RHCP and LHCP waves, respectively.

Resistive instability in a uniformly rotating magnetoplasma

1971 ◽  
Vol 6 (1) ◽  
pp. 73-85
Author(s):  
A. D. Lunn
Keyword(s):  
Magnetic Field ◽  
Growth Rates ◽  
Larmor Radius ◽  
Closed Set ◽  
Finite Larmor Radius ◽  
Integral Methods ◽  
Stabilizing Effect ◽  
Instability Growth ◽  
Linear Differential ◽  
The Stability

A closed set of guiding centre equations, derived for a rotating plasma in a static magnetic field, is applied to the problem of the stability of a plasma in a sheared field. The rotation is found to have a stabilizing effect in the absence of resistivity.A pair of coupled, linear differential equations is derived for the rotating plasma in a weakly sheared field. Dispersion relations are obtained by phase integral methods and, in the absence of finite Larmor radius effects and rotation, instability growth rates proportional to η½13 are found which become proportional to when either is included. The inclusion of both finite Larmor radius and rotation gives growing instabilities proportional to η which are stabilized by the rotation when the finite Larmor radius terms predominate.

The stability properties of cylindrical force-free fields: effect of an external potential field

1980 ◽  
Vol 24 (1) ◽  
pp. 39-53 ◽  
Author(s):  
C. Chiuderi ◽  
G. Einaudi ◽  
S. S. Ma ◽  
G. van Hoven
Keyword(s):  
Time Scales ◽  
Decay Time ◽  
Growth Rates ◽  
Potential Field ◽  
Large Scale ◽  
Stable Region ◽  
Tearing Mode ◽  
Magnetic Shear ◽  
Free Fields ◽  
The Stability

A large-scale potential field with an embedded smaller-scale force-free structure (∇ × B = αB) is studied in cylindrical geometry. We consider cases in which α goes continuously from a constant value α0 on the axis to zero at large r. Such a choice of α(r) produces fields which are realistic (few field reversals) but not completely stable. The MHD-unstable wavenumber regime is found. Since the considered equilibrium field exhibits a certain amount of magnetic shear, resistive instabilities can arise. The growth rates of the tearing mode in the limited MHD-stable region of º space are calculated, showing time-scales much shorter than the resistive decay time.

scholarly journals On the modeling of planetary plasma environments by a fully kinetic electromagnetic global model HYB-em

2010 ◽  
Vol 28 (3) ◽  
pp. 743-751 ◽  
Author(s):  
V. Pohjola ◽  
E. Kallio
Keyword(s):  
Magnetic Field ◽  
Kinetic Model ◽  
Electromagnetic Waves ◽  
Dimensional Space ◽  
Spherical Wave ◽  
Three Dimensional ◽  
Magnetized Plasma ◽  
Electromagnetic Model ◽  
The Stability ◽  
Propagation Of Waves

Abstract. We have developed a fully kinetic electromagnetic model to study instabilities and waves in planetary plasma environments. In the particle-in-a-cell (PIC) model both ions and electrons are modeled as particles. An important feature of the developed global kinetic model, called HYB-em, compared to other electromagnetic codes is that it is built up on an earlier quasi-neutral hybrid simulation platform called HYB and that it can be used in conjunction with earlier hybrid models. The HYB models have been used during the past ten years to study globally the flowing plasma interaction with various Solar System objects: Mercury, Venus, the Moon, Mars, Saturnian moon Titan and asteroids. The new stand-alone fully kinetic model enables us to (1) study the stability of various planetary plasma regions in three-dimensional space, (2) analyze the propagation of waves in a plasma environment derived from the other global HYB models. All particle processes in a multi-ion plasma which are implemented on the HYB platform (e.g. ion-neutral-collisions, chemical processes, particle loss and production processes) are also automatically included in HYB-em model. In this brief report we study the developed approach by analyzing the propagation of high frequency electromagnetic waves in non-magnetized plasma in two cases: We study (1) expansion of a spherical wave generated from a point source and (2) propagation of a plane wave in plasma. The analysis shows that the HYB-em model is capable of describing these space plasma situations successfully. The analysis also suggests the potential of the developed model to study both high density-high magnetic field plasma environments, such as Mercury, and low density-low magnetic field plasma environments, such as Venus and Mars.

scholarly journals Instability of a plane conducting free surface submitted to an alternating magnetic field

1998 ◽  
Vol 375 ◽  
pp. 65-83 ◽  
Author(s):  
Y. FAUTRELLE ◽  
A. D. SNEYD
Keyword(s):  
Magnetic Field ◽  
Free Surface ◽  
Growth Rates ◽  
Critical Magnetic Field ◽  
Hill Equation ◽  
Alternating Magnetic Field ◽  
Time Averaging ◽  
Weak Formulation ◽  
Field Frequency ◽  
The Stability

This paper considers the stability of a horizontal liquid-metal free surface in the presence of a horizontal alternating magnetic field. A weak formulation is used to derive a generalized Mathieu–Hill equation for the evolution of surface perturbations. Previous studies which rely on time-averaging the electromagnetic force over one field cycle have predicted a generally weak instability, but we find much larger growth rates near the resonances, where the surface wave frequency is an integral multiple of the field frequency. The method can be extended to include viscous and ohmic damping; the former has little effect, while the latter damps all waves except those whose frequency is close to the field frequency. Growth rates can be closely approximated by simple algebraic formulae, as can the critical magnetic field strength for the onset of instability.

scholarly journals CORONAL INSTABILITIES

1989 ◽  
Vol 8 ◽  
pp. 529-533
Author(s):  
G. Einaudi
Keyword(s):  
Thermal Conduction ◽  
Energy Equation ◽  
Dissipative Process ◽  
Mhd Equations ◽  
Present Review ◽  
Plasma Instabilities ◽  
Active Behavior ◽  
The Stability ◽  
Globally Stable ◽  
Coronal Structures

AbstractThe interest in the stability of coronal structures derives from their observed lifetime (much longer than the relevant hydromagnetic timescale) coupled with their active behavior. This fact implies that these structures must be globally stable with respect to fast and destructive instabilities and, at the same time, must allow some local, non-disrupting, dissipative process to take place. In highly magnetized media as solar and stellar coronae a large number of plasma instabilities can occur. The present review will concentrate on those governed by the magnetohydrodynamic (MHD) equations with the inclusion of the effects of finite resistivity and viscosity and the use of an energy equation where radiation, mechanical heating and thermal conduction are considered.

Hydromagnetic Instability Conditions for Viscoelastic Non-Newtonian Fluids

2000 ◽  
Vol 55 (3-4) ◽  
pp. 460-466
Keyword(s):  
Magnetic Field ◽  
Growth Rates ◽  
Stable Configuration ◽  
Horizontal Magnetic Field ◽  
Physical Conditions ◽  
Unstable Configuration ◽  
The Stability ◽  
Parameter Values ◽  
The Magnetic Field ◽  
Second Order Fluids

Abstract The effect of a horizontal magnetic field and a non-Newtonian stress tensor, as described by the Wal-ters B’ model, on the instability of two second order fluids of high kinematic viscosities and viscoelas-ticities is investigated. For the potentially stable configuration, it is found that the system is stable or unstable for a wavenumber range depending on the kinematic viscoelasticity. For the potentially un-stable configuration, it is found that the stability criterion is dependent on orientation and magnitude of the magnetic field which is found to stabilize a certain range of the unstable configuration related to the viscoelasticity values. The behaviour of growth rates with respect to Alfvén velocities are examined analytically, and it is found that the magnetic field has a dual role on the instability problem. For the exponentially varying stratifications, the system is found to be stable or unstable for the stable and un-stable stratifications under certain physical conditions, and the growth rates are found to increase or de-crease with increasing the stratification parameter values, according to some restrictions satisfied by the chosen wavenumbers range

Electromagnetic instabilities in high-β anti-loss-cone plasmas

1976 ◽  
Vol 16 (1) ◽  
pp. 73-79 ◽  
Author(s):  
B. Buti
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Growth Rates ◽  
Drift Waves ◽  
Loss Cone ◽  
The Stability ◽  
Drift Instability

The stability of electromagnetic drift waves in high-β anti-loss-cone plasmas is investigated. These waves with propagation transverse to the external magnetic field are found to be unstable provided ρ > ρc, where ρ is the parameter which characterizes the strength of the anti-loss-cone. The growth rates associated with this instability (which may be called the anti-loss-cone drift instability) are ˜ 0·1Ωe and they increase with the strength of the anti-loss-cone.

Stability of magnetohydrodynamic shock waves

1967 ◽  
Vol 1 (4) ◽  
pp. 463-472 ◽  
Author(s):  
Martin Lessen ◽  
Narayan V. Deshpande
Keyword(s):  
Magnetic Field ◽  
Mach Number ◽  
Shock Waves ◽  
Growth Rates ◽  
Acoustic Waves ◽  
Normal Mode Analysis ◽  
Mode Analysis ◽  
Magnetohydrodynamic Shock ◽  
The Stability ◽  
The Magnetic Field

The stability of oblique magnetohycirodynamic shock waves is studied with respect to a disturbance that excites magneto-acoustic waves. The problem is solved numerically by the normal mode analysis and it is shown that slow shocks are unstable in the sense that the disturbance grows exponentially with time. Growth rates are calculated for a particular Mach number and for different values of the magnetic field and obliqueness. The fast shock appears to be stable.

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