Instability of phase space tubes

An approximate analytical model is developed to study the instability of ph ase space tubes (holes extended perpendicular to B) in a 2-D magnetized pla sma. This instability has been observed in long-duration kinetic simulation s of the two-stream instability that produce bipolar electric field structu res comparable to those observed in the auroral ionosphere. The tubes are s hown to possess stable vibrational modes that become unstable when resonant ly coupled to an electrostatic whistler with parallel wavelength long compa red to the width of the tube.