  Discharge source is considered as modifier of flow hydrodynamic spectrum.
Characteristic frequency of nonlinear spectrum and spectrum power were
determined under conditions of arc sliding discharge in supersonic flow. Two
stages of discharge were defined: sliding stage and still stage. It was found
that stage transition occurs due to convective instability of discharge.
Fraction of sliding stage in overall discharge duration is determined by
averaged current that is general stable discharge parameter. This phenomenon
gives opportunity to control power of pressure fluctuations spectrum.
Theoretical insight of field and hydrodynamic factors influencing on pulsations
frequency was achieved. Hydrodynamic resistance of discharge region and holding
cathode electric field turned out to be basic factors of frequency
modification. Corresponding experimental verification was taken. Basic
frequency law was determined for several discharge regimes.
