Instability of electrons drifting through ions across a magnetic field

IT IS SHOWN THAT THE DRIFT MOTION OF THE ELECTRONS ACROSS THE IONS RESULTS IN THE USUAL TWO-STREAM INSTABILITY AND THAT THE MAGNETIC FIELD, WHILE REDUCING THE GROWTH RATE TO SOME EXTENT, IS UNABLE TO INHIBIT THE INSTABILITY EFFECTIVELY. The time scale is lengthened like B to the 1/3 power and not, as in collisional diffusion theory, like B squared. Typically, it can be predicted that if an electric field were applied to a plasma in a magnetic field, to reach its full value within a time rather less than an ion gyroperiod, the ions would never complete such a period; their interaction with the drifting electrons would have led to a state in which the ions and electrons shared their mean momentum. It is suggested that, in the case of shock or sheath models, the instability and resulting turbulence would account for the entropy change across the shock, while in PIG-type discharges it might account for the observed enhanced cross-field diffusion. (Author)