  Magnetic fields are key ingredients for heating the solar corona to
temperatures of several million Kelvin. A particularly important region with
respect to this is the so-called magnetic canopy below the corona, where sound
and Alfv\'en waves have roughly the same speed and can, therefore, easily
transform into each other. We present the results of an Alfv\'en-wave
experiment with liquid rubidium carried out in a pulsed field of up to 63 T. At
the critical point of 54 T, where the speeds of Alfv\'en waves and sound
coincide, a new 4 kHz signal appears in addition to the externally excited 8
kHz torsional wave. This emergence of an Alfv\'en wave with a doubled period is
in agreement with the theoretical predictions of a parametric resonance between
the two wave types. We also present preliminary results from numerical
simulations of Alfv\'en and magneto-sonic waves using a compressible MHD code.
