The Viking spacecraft carried a plasma wave interferometer consisting of two Langmuir probes separated by 80 m. The interferometer has measured density irregularities in the frequency range 1--200 Hz which can be interpreted as field aligned structures with phase velocities transverse to the geomagnetic field which are small compared to the spacecraft velocity relative to the plasma. The spatial structures which have nearly zero frequency in the plasma frame are Doppler shifted up to frequencies as large as 200 Hz in the spacecraft frame. The broadband amplitude of the density irregularities is typically .1% to .5%. The density irregularities appear to be a common feature of the high latitude ionosphere probed by Viking. ¿American Geophysical Union 1987