Electrohydrodynamic instabilities in dielectric liquids induced by corona discharge

Corona discharge from a needle is used to induce electrohydrodynamic (EHD) instabilities in a flat thin layer of dielectric liquid. We encounter two types of instabilities. The first one appears only for very insulating liquids and it is linked to the space charge induced in the liquid. This instability happens to be the classical EHD instability induced by unipolar injection. At higher voltages we observe a second instability in highly insulating liquids that is also observable for more conducting liquids. This second instability is due to the existence of a charged free surface.