  In this paper, we report a new type of instability of electron holes (EHs)
interacting with passing ions. The nonlinear interaction of EHs and ions is
investigated using a new theory of hole kinematics. It is shown that the
oscillation in the velocity of the EH parallel to the magnetic field direction
becomes unstable when the hole velocity in the ion frame is slower than a few
times the cold ion sound speed. This instability leads to the emission of
ion-acoustic waves from the solitary hole and decay in its magnitude. The
instability mechanism can drive significant perturbations in the ion density.
The instability threshold, oscillation frequency and instability growth rate
derived from the theory yield quantitative agreement with the observations from
a novel high-fidelity hole-tracking Particle-In-Cell (PIC) code.
