Abstract
The excitation of magnetohydrodynamic modes by hot trapped particles is studied using different kinetic distribution functions and, for the first time, a fluid model, valid in both the adiabatic and isothermal limits of the perpendicular motion, an unexpanded fluid description for the hot particles. The fluid model gives zero threshold for continuum modes but also a significant reduction in the kinetic threshold can be obtained for particular equilibria. In addition, a comparison with global modes has been made.