The current flow in the Tethered Satellite System (TSS) induces a strong excitation of electric and magnetic fluctuations in the potential sheath surrounding the subsatellite. The wave sensors of the experiment RETE (Research on Electrodynamic Tether Effects) have measured power spectra of electromagnetic fields from 180 Hz to 12 MHz, providing information on the physical processes taking place around highly charged bodies in the ionosphere and, in particular, the role of wave-particle interactions and anomalous collisionality. We report on the observations during three events of almost steady current flow at 50, 190 and 55 mA, taking place at positive satellite potentials of about 9, 200 and 2 V. The largest power spectral density occurs at frequencies between 2 and 4 kHz, close to the lower hybrid frequency, where electric field fluctuations up to 12 V/m have been observed. In this frequency band the fields are electrostatic and radially polarized, with a marked ram-wake signature. ¿ 1998 American Geophysical Union