Acceleration of relativistic electrons due to resonant scattering by whistler mode waves generated by temperature anisotropy in the inner magnetosphere

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.

Download Full-text

Study of whistler mode instability in Saturn's magnetosphere

Annales Geophysicae ◽

10.5194/angeo-24-1705-2006 ◽

2006 ◽

Vol 24 (6) ◽

pp. 1705-1712 ◽

Cited By ~ 14

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.

Download Full-text

The effect of electron and ion temperature on the refractive index surface of 1-10 kHz whistler mode waves in the inner magnetosphere

Journal of Geophysical Research Space Physics ◽

10.1002/2014ja020669 ◽

2015 ◽

Vol 120 (1) ◽

pp. 581-591 ◽

Cited By ~ 10

Author(s):

P. Kulkarni ◽

M. Gołkowski ◽

U. S. Inan ◽

T. F. Bell

Keyword(s):

Refractive Index ◽

Ion Temperature ◽

Inner Magnetosphere ◽

Whistler Mode ◽

Whistler Mode Waves

Download Full-text

Electron-scale sheets of whistlers close to the magnetopause

Annales Geophysicae ◽

10.5194/angeo-23-3715-2005 ◽

2005 ◽

Vol 23 (12) ◽

pp. 3715-3725 ◽

Cited By ~ 12

Author(s):

G. Stenberg ◽

T. Oscarsson ◽

M. André ◽

A. Vaivads ◽

M. Morooka ◽

...

Keyword(s):

High Energy ◽

Diffusion Region ◽

Temperature Anisotropy ◽

Whistler Mode ◽

Plasma Drift ◽

High Energy Electrons ◽

Whistler Mode Waves ◽

Thin Electron ◽

Field Lines ◽

The Waves

Abstract. Whistler emissions close to the magnetopause on the magnetospheric side are investigated using the four Cluster spacecraft. The waves are found to be generated in thin (electron-scale) sheets moving with the plasma drift velocity. A feature in the electron data coincides with the waves; hot magnetospheric electrons disappear for a few satellite spins. This produces or enhances a temperature anisotropy, which is found to be responsible for the generation of the whistler mode waves. The high energy electrons are thought to be lost through the magnetopause and we suggest that the field lines, on which the waves are generated, are directly connected to a reconnection diffusion region at the magnetopause.

Download Full-text