scholarly journals Study of Oblique Propagating Whistler Mode Waves in Presence of Parallel DC Electric Field in Magnetosphere of Saturn

2017 ◽  
Vol 6 (2) ◽  
pp. 26 ◽  
Author(s):  
R. Kaur ◽  
R. S. Pandey
Keyword(s):  
Growth Rate ◽  
Distribution Function ◽  
Energy Density ◽  
Wave Number ◽  
Number Density ◽  
Temperature Anisotropy ◽  
Loss Cone ◽  
Whistler Mode ◽  
Whistler Mode Waves ◽  
Magnetosphere Of Saturn

In this paper whistler mode waves have been investigated in magnetosphere of Saturn. The derivation for perturbed distribution function, dispersion relation and growth rate have been determined by using the method of characteristic and kinetic approach. Analytical expressions for growth rate and real frequency of whistlers propagating oblique to magnetic field direction are attained. Calculations have been performed at 6 radial distances in plasma sheet region of Saturn’s magnetosphere as per data provided by Cassini. Work has been extended for bi-Maxwellian as well as Loss-cone distribution function. Parametric analysis show that temperature anisotropy, increase in number density, energy density and angle of propagation increases the growth rate of whistler waves along with significant shift in wave number. In case of Loss-cone distribution, increase in growth rate of whistlers is significantly more than for bi-Maxwellian distribution function. Generation of second harmonics can also be seen in the graphs plotted. It is concluded that parallel DC field stabilizes the wave and temperature anisotropy, angle of propagation, number density and energy density of electrons enhances the growth rate. Thus the results are of importance in analyzing observed VLF emissions over wide spectrum of frequency range in Saturnian magnetosphere. The analytical model developed can also be used to study various types of instabilities in planetary magnetospheres. 

scholarly journals Impact of hot injected beam on whistler mode with alternating electric field (AC) in the magnetosphere of Saturn

2021 ◽  
Vol 2062 (1) ◽  
pp. 012019
Author(s):  
Kumari Neeta Shukla ◽  
Devi Singh ◽  
R S Pandey
Keyword(s):  
Growth Rate ◽  
Distribution Function ◽  
Electric Field ◽  
Particle Interaction ◽  
Wide Frequency Range ◽  
Temperature Anisotropy ◽  
Mode Instability ◽  
Whistler Mode ◽  
Plasma Injection ◽  
Magnetosphere Of Saturn

Abstract Whistlers are believed to be generated by its own and responsible to evolve dynamical properties of magnetized planetary environment. Growing whistler instability can cause other uncertainties in the magnetosphere and evident to be generated by mean of injection events and temperature variance in plasma environment. In this paper the empirical dispersion relation has developed for parallel propagating whistler mode instability in an infinite saturnian magneto plasma in the presence of perpendicular electric field for ring distribution function having non-monotonous nature. Method of characteristics solutions alongside kinetic approach found to be most suitable in order to achieve perturbed plasma states. The perturbed and unperturbed particle trajectories have taken into consideration to determine perturbed distribution function. A remarkable growth rate expression with added hot plasma injection has been calculated in inner magnetosphere near 6.18 Rs. The results obtained using demonstrative value of the parameters suited to the Saturnian magnetosphere have been computed and discussed. Pressure (Temperature) anisotropy is found to be a peculiar source of free energy for whistler mode instability. The AC frequency irrespective of its magnitude, affects the growth rate significantly. The bulk of energetic hot electrons injection influences the growth rate by increasing its peak value. The result obtained provide the important view of wave particle interaction and useful to analyze the VLF emissions observed over a wide frequency range.

scholarly journals Beam effect on electromagnetic ion-cyclotron waves with general loss – cone distribution function in an anisotropic plasma-particle aspect analysis

2007 ◽  
Vol 25 (2) ◽  
pp. 557-568 ◽  
Author(s):  
G. Ahirwar ◽  
P. Varma ◽  
M. S. Tiwari
Keyword(s):  
Growth Rate ◽  
Distribution Function ◽  
Ion Beam ◽  
Temperature Anisotropy ◽  
Loss Cone ◽  
Thermal Anisotropy ◽  
Ion Cyclotron ◽  
Electromagnetic Ion Cyclotron Waves ◽  
The Waves ◽  
Emic Waves

Abstract. The effect of upgoing ion beam and temperature anisotropy on the dispersion relation, growth rate, parallel and perpendicular resonant energies, and marginal instability of the electromagnetic ion cyclotron (EMIC) waves, with general loss-cone distribution function, in a low β homogeneous plasma, is discussed by investigating the trajectories of the charged particles. The whole plasma is considered to consist of resonant and non-resonant particles. The resonant particles participate in an energy exchange with the waves, whereas the non-resonant particles support the oscillatory motion of the waves. The effects of the steepness of the loss-cone distribution, ion beam velocity, with thermal anisotropy on resonant energy transferred, and the growth rate of the EMIC waves are discussed. It is found that the effect of the upgoing ion beam is to reduce the energy of transversely heated ions, whereas the thermal anisotropy acts as a source of free energy for the EMIC waves and enhances the growth rate. It is found that the EMIC wave emissions occur by extracting energy of perpendicularly heated ions in the presence of an upflowing ion beam and a steep loss-cone distribution function in the anisotropic magnetoplasma. The effect of the steepness of the loss-cone is also to enhance the growth rate of the EMIC waves. The results are interpreted for EMIC emissions in the auroral acceleration region.

scholarly journals Study of whistler mode instability in Saturn's magnetosphere

2006 ◽  
Vol 24 (6) ◽  
pp. 1705-1712 ◽  
Author(s):  
R. P. Singhal ◽  
A. K. Tripathi
Keyword(s):  
Diffusion Coefficients ◽  
Pitch Angle ◽  
Temperature Anisotropy ◽  
Mode Instability ◽  
Whistler Mode ◽  
Energy Diffusion ◽  
Whistler Mode Waves ◽  
Magnetosphere Of Saturn ◽  
Temporal Growth Rate ◽  
Good Agreement

Abstract. A dispersion relation for parallel propagating whistler mode waves has been applied to the magnetosphere of Saturn and comparisons have been made with the observations made by Voyager and Cassini. The effect of hot (suprathermal) electron-density, temperature, temperature anisotropy, and the spectral index parameter, κ, on the temporal growth rate of the whistler mode emission is studied. A good agreement is found with observations. Electron pitch angle and energy diffusion coefficients have been obtained using the calculated temporal growth rates.

Effect of the general loss-cone distribution function on kinetic Alfvén waves—a kinetic approach

2007 ◽  
Vol 73 (6) ◽  
pp. 911-920 ◽  
Author(s):  
NIDHI SHUKLA ◽  
P. VARMA ◽  
M.S. TIWARI
Keyword(s):  
Growth Rate ◽  
Distribution Function ◽  
Alfven Waves ◽  
Wave Frequency ◽  
Kinetic Approach ◽  
Wave Number ◽  
Alfvén Waves ◽  
Ion Temperature ◽  
Loss Cone ◽  
Kinetic Alfvén Waves

AbstractKinetic Alfvén waves are investigated in the presence of a general loss-cone distribution function including finite electron pressure and ion-gyroradius effects. The dispersion relation and damping/growth rate are evaluated for different electron to ion temperature ratios, Te/Ti, using a kinetic approach. The wave frequency ω and damping/growth rate γL are evaluated for two regimes of propagation, k⊥ρi < 1 and k⊥ρi > 1, where k⊥ is the perpendicular wave number and ρi is the ion-gyroradius. An enhancement of the wave frequency and a reduction in the damping rate are predicted by steep loss-cone distribution indices and Te/Ti. The growth of the wave is also noticed at higher values of the distribution index and lower Te/Ti. Plasma parameters appropriate to the plasma sheet boundary layer (PSBL) are used to discuss the propagation of kinetic Alfvén waves from the PSBL to the auroral ionosphere.

Electron whistler mode instability in an inhomogeneous thermal plasma in the presence of an inhomogeneous beam of suprathermal electrons

1983 ◽  
Vol 29 (3) ◽  
pp. 439-448 ◽  
Author(s):  
H.A. Shah ◽  
V.K. Jain
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Dispersion Relation ◽  
Thermal Plasma ◽  
Uniform Magnetic Field ◽  
Inhomogeneous Plasma ◽  
Mode Instability ◽  
Whistler Mode ◽  
Suprathermal Electrons ◽  
Whistler Mode Waves

The excitation of the whistler mode waves propagating obliquely to the constant and uniform magnetic field in a warm and inhomogeneous plasma in the presence of an inhomogeneous beam of suprathermal electrons is studied. The full dispersion relation including electromagnetic effects is derived. In the electrostatic limit the expression for the growth rate is given. It is found that the inhomogeneities in both beam and plasma number densities affect the growth rates of the instabilities.

Comparison of quasi-linear predictions with a computer simulation of whistler waves in unstable plasmas

1974 ◽  
Vol 11 (3) ◽  
pp. 397-401 ◽  
Author(s):  
S. Cuperman ◽  
L. R. Lyons
Keyword(s):  
Growth Rate ◽  
Computer Simulation ◽  
Distribution Function ◽  
Mode Coupling ◽  
Simulation Experiment ◽  
Electron Distribution Function ◽  
Linear Wave ◽  
Wave Growth ◽  
Whistler Mode Waves ◽  
Computer Simulation Experiment

The quasi-linear concept of plateau formation along resonant diffusion surfaces is compared with the time evolution of the electron distribution function during a computer simulation experiment of whistler-mode waves in unstable plasmas. It is found that, as the wave intensities grow, plateau formation does indeed occur, with the distribution function becoming constant along diffusion surfaces at the time when wave intensities maximize. Following the formation of the plateaus, both the wave intensities and the slope of the distribution function along diffusion surfaces oscillate in a manner suggesting msh;mode coupling. Tbe slope of the distribution function along diffusion surfaces, which controls the linear wave growth rate, also gives good predictions of the sign of the actual wave growth rate during the experiment.

Spatial stability of the non-parallel Bickley jet

1981 ◽  
Vol 102 ◽  
pp. 127-140 ◽  
Author(s):  
Vijay K. Garg
Keyword(s):  
Growth Rate ◽  
Energy Density ◽  
Critical Reynolds Number ◽  
Transverse Velocity ◽  
Parallel Flow ◽  
Wave Number ◽  
Amplitude Wave ◽  
Spatial Stability ◽  
Rate Dependent ◽  
Neutral Curves

The spatial stability of the plane, two-dimensional jet flow to infinitesimal disturbances is investigated by taking into account the effects of transverse velocity component and the streamwise variations of the basic flow and of the disturbance amplitude, wave-number and spatial growth rate. This renders the growth rate dependent on the flow variable as well as on the transverse and streamwise co-ordinates. Growth rates for the energy density of the disturbance and the associated neutral curves are provided as a function of the streamwise co-ordinate. Variation of growth rate of the disturbance stream function and streamwise component of velocity with the transverse co-ordinate is also given for different disturbance frequencies and streamwise locations. Results are compared with those for the parallel-flow stability analysis, and also with those for an analysis that accounts for only some of the non-parallel effects. It is found that the critical Reynolds number based on the growth of energy density of the disturbance depends on the streamwise co-ordinate and lies within the range (around 20) found experimentally, while the parallel-flow theory yields a rather low value of 4·0.

Instability of whistler-mode waves by a relativistic kappa-loss-cone distribution in space plasmas

2006 ◽  
Vol 48 (9) ◽  
pp. 1437-1445 ◽  
Author(s):  
Fuliang Xiao ◽  
Qinghua Zhou ◽  
Huiyong He ◽  
Lijun Tang
Keyword(s):  
Space Plasmas ◽  
Loss Cone ◽  
Whistler Mode ◽  
Whistler Mode Waves
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