Oscillations in P.I.G. Discharge and A Type of Instability of Plasma

An explanation is presented for the existence of hydromagnetic waves in a partialiy ionized gas discharge that do not damp in a weak magnetic field and tend to have a phase velocity of the sound wave in a stronger field. Equation for a low frequency osciliation with smali amplitude in a plasma in a uniform magnetic field are used in the analysis. (C.E.S.)