  We apply an eclipse mapping technique to observations of the eclipsing
magnetic cataclysmic variable HU Aqr. The observations were made with the
S-Cam2 Superconducting Tunnel Junction detector at the WHT in October 2000,
providing high signal-to-noise observations with simultaneous spectral and
temporal resolution. HU Aqr was in a bright (high accretion) state (V=14.7) and
the stream contributes as much to the overall system brightness as the
accretion region on the white dwarf. The stream is modelled assuming accretion
is occuring onto only one pole of the white dwarf. We find enhanced brightness
towards the accretion region from irradiation and interpret enhanced brightness
in the threading region, where the ballistic stream is redirected to follow the
magnetic field lines of the white dwarf, as magnetic heating from the
stream-field interaction, which is consistent with recent theoretical results.
Changes in the stream eclipse profile over one orbital period indicate that the
magnetic heating process is unstable.
