ELECTRON-CYCLOTRON MASER EMISSION AT OBLIQUE ANGLES

Observations of elliptically polarized bursts of decametric radio emis sion from Jupiter with axial ratios of the polarization ellipse 0.2 le ss than or similar T less than or similar 0.7 imply emission at angles 45-degrees- less than or similar theta less than or similar 80-degree s to the magnetic field. Emission at oblique angles less than or simil ar 60-degrees is not expected in the conventional theory of electron c yclotron maser emission. It is argued that electron cyclotron emission at a given theta requires electrons with parallel velocity concentrat ed around upsilon(parallel-to) = upsilon cos alpha = c cos theta. A me chanism is proposed that might produce an appropriate ''spiraling beam '' distribution, with a peak in velocity space at speed upsilon = upsi lon0 and pitch angle alpha = alpha0 not-equal 0.