Upconversion of whistler
waves by gyrating ion
beams in a plasma
HARSHA JALORI, SUNIL K SINGH and A K GWAL*
Space Science Laboratory, Department of
Physics and Electronics, Barkatullah University,
Bhopal 462 026, India
*Corresponding author
E-mail: splakg@sancharnet.in
Abstract. A gyrating ion beam, with a ring-shaped distribution in velocity,
supports
negative energy beam modes near the harmonics
of beam gyro-frequency. An investigation
of the non-linear interaction of
high-frequency whistler waves with the negative energy
beam cyclotron mode is made. A non-linear
dispersion relation is derived for the coupled
modes. It is shown that a gyrating ion-beam
frequency upconverts the whistler waves
separated by harmonics of beam gyro-frequency.
The expression for the growth rate of
whistler mode waves has been derived. In Case
1, a high-amplitude whistler wave decays
into two lower frequency waves, called a
low-frequency mode and a side band of frequency
lower than that of pump wave. In Case 2 a
high-amplitude whistler wave decays into
two lower frequency daughter waves, called the
low-frequency mode and whistler waves.
Generation mechanism of these waves has
application in space and laboratory plasmas.
Keywords. Electromagnetic waves; magnetic field; whistler.