Perturbed electromagnetic field and Poynting flux of kinetic Alfvén waves in kappa distributed space plasmas

Abstract.

Kappa distribution is frequently observed in the space plasmas. Also, in these plasmas, fluctuations of the perturbed electromagnetic field and Poynting flux associated with kinetic Alfvén waves (KAWs) have been regularly measured. To date, the fluctuations have only been ascribed to the gyroradius correction terms in Maxwellian distributed plasmas. In this paper, using kinetic theory with the choice of kappa distribution, it is suggested that the aforesaid fluctuations may be attributed to the non-thermal features characterized by the index $\kappa$. The generalized results incorporate an infinite range of the spectral index $\kappa$, where the small and the infinitely large values of $\kappa$ correspond to suprathermal and Maxwellian plasmas, respectively. The small values of $\kappa$, as compared to Maxwellian plasma, are found beneficial for energizing the plasma over long distances in the direction of ambient magnetic field that would probably lead to the generation of electron beam which may, in turn, find applications in the auroral emission and broadband electrostatic noise.