Linear Dispersion Theory Of Parallel Electromagnetic Modes For Regularized Kappa-Distributions

The velocity particle distributions measured in situ in space plasmas deviate from Maxwellian (thermal) equilibrium, showing enhanced suprathermal tails that are well described by the standard Kappa-distribution (SKD). Despite its successful application, the SKD is frequently disputed due to a series of unphysical implications such as diverging velocity moments, preventing a macroscopic description of the plasma. The regularized Kappa-distribution (RKD) has been introduced to overcome these limitations, but the dispersion properties of RKD-plasmas have not yet been explored. In the present paper, we compute the wavenumber dispersion of the frequency and damping or growth rates for the electromagnetic modes in plasmas characterized by the RKD. This task is accomplished by using the grid-based kinetic dispersion solver LEOPARD ("Linear Electromagnetic Oscillations in Plasmas with Arbitrary Rotationally symmetric Distributions") developed for arbitrary gyrotropic distributions [P. Astfalk and F. Jenko, J. Geophys. Res. 122, 89 (2017)]. By reproducing previous results obtained for the SKD and Maxwellian, we validate the functionality of the code. Furthermore, we apply the isotropic and anisotropic RKDs to investigate stable electromagnetic electron-cyclotron (EMEC) and ion-cyclotron (EMIC) modes, as well as temperature-anisotropy-driven instabilities, for bothT perpendicular to /T parallel to > 1 (EMEC and EMIC instabilities) andT perpendicular to /T parallel to < 1 cases (proton and electron firehose instabilities), where andperpendicular to denote directions parallel and perpendicular to the local time-averaged magnetic field. Provided that the cutoff parameter alpha is small enough, the results show that the RKDs reproduce the dispersion curves of the SKD plasmas at both qualitative and quantitative levels. For higher values, however, a physically significant deviation occurs.