Kinetic Alfven solitary and rogue waves in superthermal plasmas

We investigate the small but finite amplitude solitary Kinetic Alfven waves (KAWs) in low beta plasmas with superthermal electrons modeled by a kappa-type distribution. A nonlinear Korteweg-de Vries (KdV) equation describing the evolution of KAWs is derived by using the standard reductive perturbation method. Examining the dependence of the nonlinear and dispersion coefficients of the KdV equation on the superthermal parameter kappa, plasma beta, and obliqueness of propagation, we show that these parameters may change substantially the shape and size of solitary KAW pulses. Only sub-Alfvenic, compressive solitons are supported. We then extend the study to examine kinetic Alfven rogue waves by deriving a nonlinear Schrodinger equation from the KdV equation. Rational solutions that form rogue wave envelopes are obtained. We examine how the behavior of rogue waves depends on the plasma parameters in question, finding that the rogue envelopes are lowered with increasing electron superthermality whereas the opposite is true when the plasma beta increases. The findings of this study may find applications to low beta plasmas in astrophysical environments where particles are superthermally distributed. (C) 2014 AIP Publishing LLC.