  This is a report about a comparison of collisionless simulations on global
modes (i.e. low poloidal mode number) with gyrokinetic code NEMORB against
analytical theory and other codes. Only axisymmetric modes, i.e. with toroidal
mode number n=0, are considered, and flat equilibrium profiles. Benchmarks are
performed for GAMs against local analytical theory. In the presence of
energetic ions, local benchmarks of NEMORB are performed against semilagrangian
gyrokinetic code GYSELA. The models of adiabatic vs trapped-kinetic- vs
fully-kinetic-electrons and of electrostatic vs electromagnetic at very low
beta are compared. Scalings of Alfven modes are also presented.
