Low-Frequency Instabilities in Magnetic Pulses

Electrons drifting relative to ions across a magnetic field are found to drive a set of intermediate-frequency long-wavelength waves (${\ensuremath{\omega}}_{\mathrm{ci}}<\ensuremath{\omega}<{\ensuremath{\omega}}_{\mathrm{ce}}$) unstable for any temperature ratio $\frac{{T}_{e}}{{T}_{i}}$ One instability is caused by the coupling of a drift wave in a nonuniform plasma to either the ion plasma oscillation or a lower hybrid oscillation, depending on density and field strength. Another instability is a form of the two-stream instability, shown here to exist even for drift speeds less than electron thermal speeds. Growth rates are on the order of the ion plasma (or lower hybrid) frequency, depending on the density and field strength.