The cyclotron maser instability : application to low-density magnetoplasmas

The cylcotron maser instability is applied to low-density magnetoplasmas to derive simple expressions relating the wave-emergent angle of the amplified wave (theta) and the ratio f/f(c) at the source to the normalized (to the light velocity c) parallel bulk velocity (PBV) of the instability (characteristic for an auroral electron distribution function). It is shown that, for PBV corresponding to 1-10 keV, theta is nearly perpendicular with respect to the magnetic field and is decreasing as PBV increases. The results are highly relevant to the lower-frequency auroral emission of Jupiter and Saturn. 21 refs.