Analysis of Voyager plasma wave data from the Jovian foreshock has revealed the existence of a new oscillation with center frequency below fp and typically lying above the upper limit Doppler shift frequency for ion acoustic waves. The properties of these waves are consistent with modes generated by a strong electron heat flux in an unmagnetized plasma. Such modes become unstable when the effective drift velocity exceeds (nCOLD/nHOT)1/2 times the thermal speed of the hot component. The occasional simultaneous appearance of more than one frequency band is a possible indication of multiple magnetic connection with the shock.