Measurements from rocket borne sensors inside a high velocity neutral barium beam show a factor of six increase in plasma density in a moving ionizing front. This region was co-located with intense fluctuating electric fields (ΔE≈300 mV/m) at frequencies well under the lower hybrid frequency for a barium plasma. Large quasi-DC electric and magnetic field fluctuations were also detected with a large component of the current and the electric field parallel to Bo. An Alfv¿n wave with a finite electric field component parallel to the geomagnetic field was observed to propagate along Bo, where it was detected by an instrumented sub-payload. ¿ American Geophysical Union 1990