  Aims. We investigate the transfer of energy between a standing kink mode and
azimuthal Alfven waves within an expanding flux tube. We consider the process
of resonant absorption in a loop with a non-uniform Alfven frequency profile
but in the absence of a radial density gradient. Methods. Using the MHD code,
Lare3d, we model an oscillating magnetic flux tube that expands radially with
height. An initially straight loop structure with a magnetic field enhancement
is relaxed towards a force-free state before a standing kink mode is
introduced. Results. We demonstrate that the transverse gradient in Alfven
frequency required for the existence of resonant field lines can be associated
with the expansion of a high field-strength flux tube from concentrated flux
patches. This allows for the conversion of energy between wave modes even in
the absence of the density profile typically assumed in wave heating models. As
with standing modes in straight flux tubes, small scales are dominated by the
vorticity at the loop apex and by currents at the foot points. The azimuthal
wave exhibits the structure of the expanded flux tube and is therefore
associated with smaller length scales close to the foot points of the flux
tube. Conclusions. Resonant absorption can proceed throughout the corona, even
in the absence of dense loop structures. The flux tube and MHD waves considered
are difficult to observe and our model highlights how estimating hidden wave
power within the solar atmosphere can be problematic. We highlight that, for
standing modes, the global properties of field lines are important for resonant
absorption and coronal conditions at a single altitude will not fully determine
the nature of MHD resonances. We provide a new model in partial response to the
criticism that wave heating models cannot self-consistently generate or sustain
the density profile upon which they typically rely.
