The cometary plasma environment at low gas production rates is dominated
by highly compressional, large amplitude magnetic field waves in the
10-100mHz range. They are thought to be caused by an ion-Weibel
instability due to a cross-field current, which is caused by the
cometary ions that are accelerated along the solar wind convective
electric field. We devise a new method to determine the location of the
wave detection, the wave power, frequency, and bandwidth. It is found
that the wave occurs everywhere in the coma, regardless of electric
field direction. There is no correlation between the wave frequency and
the measured plasma density. This is not in agreement with previous
studies. A dependence of the frequency on the position of the spacecraft
in a comet-fixed frame is in agreement with the prediction from the
ion-Weibel instability. We infer a wave generation region much larger
than the distances covered by Rosetta.