ABSTRACT
This chapter presents an expression for the compressible part of the perturbed trapped-particle pressure. This expression is proportional to an average of the perturbed plasma displacement multiplied by the magnetic-field curvature over the bounce period. The chapter considers the description of the small-scale modes allowing for the trapped-particle contribution. It calculates the trapped-particle contribution into the potential energy of kink modes. The stabilization effect of trapped particles was initially studied in the problem of interchange modes. The chapter outlines trapped particles to be collisionless. Such an assumption is valid if the growth rate is large compared with the effective collision frequency of the corresponding species of trapped particles.
