Abstract
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.
Highlights
Magnetized plasma supports a variety of plasma waves
Since the electrons are accelerated more effectively by electromagnetic waves at frequencies of few kilohertz [17], increasing the growth rate, we investigate whistler mode waves in presence of parallel DC electric field in magnetosphere of Saturn in present work
Analyzing the results drawn from expression of growth rate and all the graphs plotted in presence of parallel DC field, it can be concluded that magnitude of growth rate of whistler mode waves in case of Loss-cone distribution function is much more than in case of bi-Maxwellian distribution function
Summary
Magnetized plasma supports a variety of plasma waves. The investigations done in planet’s orbit have shown two general classes of wave-particle interactions, controlling the important aspects of plasma dynamics in magnetospheres, namely, electromagnetic and electrostatic plasma instabilities. Whistler mode emission constitutes electromagnetic waves with frequency below either electron gyro frequency or local electron plasma frequency, whatever is less Since these low frequency whistler mode waves interact with charged particles over long scale lengths within magnetospheres and transfer energy from one region to another, we chose to study them using Electromagnetic Theory. Accelerating charged particles to kinetic energies much higher than their initial thermal energy is one of the significant phenomena effecting the dynamics of planetary magnetospheres and ionospheres It can be understood by studying the exchange of mass and energy through electric field parallel to magnetic field [13,14,15]. Since the electrons are accelerated more effectively by electromagnetic waves at frequencies of few kilohertz [17], increasing the growth rate, we investigate whistler mode waves in presence of parallel DC electric field in magnetosphere of Saturn in present work. Parametric analysis has been done by calculating the growth rate of whistler mode waves
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