Coherent cyclotron maser radiation from UV Ceti

Recent images in the radio of UV Ceti show two intense emission regions abo ve the magnetic poles of the star. The emission is overwhelmingly right han d circularly polarized with 100% right hand polarization at 3 cm and 6 cm w avelengths during flares. This high degree of polarization rules out gyrosy nchrotron emission. In this article we propose that such emission can be pr oduced by a coherent cyclotron maser driven by field aligned electrons movi ng into an increasing magnetic field. Conservation of the first adiabatic i nvariant causes the electron beam to increase its pitch angle. This produce s a broad region on the distribution function and the possibility of produc ing a positive slope in the perpendicular velocity space. Such distribution functions are common in magnetic mirror type geometries and are possible s ources of free energy leading to electromagnetic emission by a cyclotron ma ser instability mechanism.