Ground-based magnetometer observations are used to confirm the properties of a large azimuthal wave number Pc 5 pulsation observed previously with the STARE radar. The magnetometer and STARE results allow an estimate to be made of the ionospheric height-integrated Hall conductivity, as well as supporting theories that predict 90¿ rotation of polarization between ionosphere and ground. The properties of the observed vertical magnetic component at the ground are also found to be consistent with recent theory.