We discuss a new model to describe the heating of the magnetically open sol
ar corona and the acceleration of the fast solar wind by the cyclotron reso
nant interaction of coronal ions with ion-cyclotron waves. This 'kinetic sh
ell' model includes important details of the wave-particle interaction whic
h are not present in most other treatments. In this model, we approximate t
he evolution of the collisionless coronal ion distribution through the assu
mption that the pitch-angle scattering by the resonant ion-cyclotron waves
is much faster than the other processes taking place. Under this assumption
, the resonant ions uniformly populate velocity-space surfaces, or shells,
of constant energy in the frame moving with the wave phase speed. We show t
hat a fast solar wind can be generated by this process. Furthermore, we pre
sent a number of properties of the resonant interaction that are implied by
this model: (1) The amount of wave energy that can be absorbed by the prot
on distribution at a given radial position is limited. (2) The proton distr
ibution generated by the interaction with outward-propagating waves will ne
cessarily be unstable to the generation of inward-propagating waves, so a c
omplete description must include waves of both propagation directions. (3)
The structure of the resonant shells for ions heavier than protons indicate
s that these ions will be perpendicularly heated by the second-order Fermi
process, an energization channel that is not available to the protons. This
last point is particularly intriguing, and may lead to a fundamentally new
way to produce the preferential effects on heavy ions in the fast solar wi
nd.