Whistler instability in non-Maxwellian plasmas

A linear analysis is carried out for whistler instability in a magnetized plasma, with the propagation direction parallel to the background magnetic field. Detailed properties of this instability are investigated for the non-Maxwellian distribution functions having high energy tails or broad shoulders as it occurs in many space plasmas environments. In particular, analytical expressions of the dielectric constant are derived for the Maxwellian, kappa (kappa) and (r, q) velocity distributions. In general, when (i) kappa -> infinity and (ii) r = 0, q -> infinity, the results approach the standard Maxwellian situation. The growth rate is suppressed for small values of kappa and q (keeping r fixed), whereas for negative values of r (keeping q fixed), instability transforms into damping. The graphic representation shows that while the L-wave has a resonance at omega = omega(L), the R-wave has a cutoff point at Omega and omega(R). Thus while the L-wave shows a behavior similar to the ordinary L-wave, the R-wave behavior is drastically changed. The whistler mode region (omega < Omega) also exhibits a changed character and thus may have important implications for the study of ionospheric phenomena.