Brown dwarfs and low-mass stars are commonly variable in the near infrared and optical wavebands. This variability has commonly been interpreted as a manifestation of variable dust cloud patterns on the surfaces of UCDs - i.e weather.

However, radio observations have revealed bright bursts, similar in nature to auroral planetary radio bursts. In this talk we present detailed studies of optical variability on very low mass stars, which show that it is also caused by the presence of extra-solar aurorae, approximately ten-thousand times more powerful than those seen on Jupiter.