Drift kink instability in the current sheet with a kappa-distribution

Superthermal particle distributions well-described by the family of kappa-distributions have been observed in various astrophysical plasmas. In this paper, the drift kink instability in the current sheet with a kappa-distribution is investigated in the framework of linear kinetic theory. The orbit integrals are treated numerically using the exact unperturbed particle orbits, and the resulting eigenvalue problem of the integro-differential equations is solved using the spectral method. The growth rate, eigenmode structure, and parametric dependencies of the kink mode are examined and compared with the case of the standard Harris current sheet. The results show that the drift kink instability in the kappa-distribution current sheet resembles its counterpart in the standard Harris sheet, but has a smaller growth rate and real frequency for small value of kappa. It is also demonstrated that a background population can enhance the growth rate of the kink mode, making the growth rate significant at the physical value of the ion-electron mass ratio. (C) 2008 American Institute of Physics.