Experimental observations are presented of the magnetically guided Alf
ven wave excited directly by a small dipole loop antenna located in th
e scrape-off layer of a tokamak plasma. This wave is excited most effi
ciently by antenna current elements aligned along the magnetic field a
nd measurements indicate that, at all frequencies below the ion cyclot
ron frequency. the wave propagates for several transits around the mac
hine with a high degree of localisation about magnetic field lines int
ersecting the antenna. Along the field, the wave has both a slowly var
ying amplitude and phase with predominantly radial electric and azimut
hal magnetic field components. These experiments demonstrate that the
Alfven wave can propagate as a magnetically guided TEM mode in plasmas
which are highly inhomogeneous. We also present a simplified mathemat
ical description of the wave.