  Recently, a number of ultracool dwarfs have been found to produce periodic
radio bursts with high brightness temperature and polarization degree; the
emission properties are similar to the auroral radio emissions of the
magnetized planets of the Solar System. We simulate the dynamic spectra of
radio emission from ultracool dwarfs. The emission is assumed to be generated
due to the electron-cyclotron maser instability. We consider two source models:
the emission caused by interaction with a satellite and the emission from a
narrow sector of active longitudes; the stellar magnetic field is modeled by a
tilted dipole. We have found that for the dwarf TVLM 513-46546, the model of
the satellite-induced emission is inconsistent with the observations. On the
other hand, the model of emission from an active sector is able to reproduce
qualitatively the main features of the radio light curves of this dwarf; the
magnetic dipole seems to be highly tilted (by about 60 degrees) with respect to
the rotation axis.
