The radial localization of the drift Alfv¿n ballooning modes (DABM), proposed by Chen and Hasegawa [1991> to explain Pc 4--5 pulsations excited by highly energetic ring current protons, is examined by using WKB approximations in the radial direction. The problem is reduced to two nested one-dimensional ones, one along the equilibrium magnetic field lines and the other in the radial direction. By ignoring kinetic effects to lowest order it is found that a localization potential well can exist for sufficiently strong earthward pressure gradient (the outer edge of the ring current). However, mode energy tunnels through a finite barrier and gets absorbed at the field line resonance layer, thereby causing damping of the global mode. This damping process imposes a minimum azimuthal mode number for the mode to be localized. The bounce-drift resonance of highly energetic protons is treated perturbatively. The results further support the theoretical picture that antisymmetric high-azimuthal mode-number drift Alfv¿n-ballooning modes are a good candidate instability mechanism for internally excited geomagnetic pulsations. ¿ American Geophysical Union 1996