Discrete emissions at the lower hybrid frequency are often seen on the S3-3 satellite. Simultaneous observation of perpendicularly heated ions suggests that ions may provide the free energy necessary to drive the instability. Studies of the dispersion relation for k∥ = 0 modes excited by warm ion rings in velocity space show that waves are excited with real frequencies near the lower hybrid frequency and with growth rates ranging from ~0.01 to 1 times the ion cyclotron frequency. Numerical results are therefore consistent with the possibility that the observed ions are the free energy source for the observed waves.